diff --git a/app/Api/V1/Controllers/Models/Rule/ExpressionController.php b/app/Api/V1/Controllers/Models/Rule/ExpressionController.php
new file mode 100644
index 0000000000..8019919161
--- /dev/null
+++ b/app/Api/V1/Controllers/Models/Rule/ExpressionController.php
@@ -0,0 +1,51 @@
+<?php
+/*
+ * ExpressionController.php
+ * Copyright (c) 2024 Michael Thomas
+ *
+ * This file is part of Firefly III (https://github.com/firefly-iii).
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+namespace FireflyIII\Api\V1\Controllers\Models\Rule;
+
+use FireflyIII\Api\V1\Controllers\Controller;
+use FireflyIII\Api\V1\Requests\Models\Rule\ValidateExpressionRequest;
+use Illuminate\Http\JsonResponse;
+
+/**
+ * Class ExpressionController
+ */
+class ExpressionController extends Controller
+{
+    /**
+     * This endpoint is documented at:
+     * https://api-docs.firefly-iii.org/?urls.primaryName=2.0.0%20(v1)#/rules/validateExpression
+     *
+     * @param ValidateExpressionRequest $request
+     *
+     * @return JsonResponse
+     *
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function validateExpression(ValidateExpressionRequest $request): JsonResponse
+    {
+        return response()->json([
+            "valid" => true,
+        ]);
+    }
+}
diff --git a/app/Api/V1/Requests/Models/Rule/StoreRequest.php b/app/Api/V1/Requests/Models/Rule/StoreRequest.php
index dff5c76d8d..669604a99a 100644
--- a/app/Api/V1/Requests/Models/Rule/StoreRequest.php
+++ b/app/Api/V1/Requests/Models/Rule/StoreRequest.php
@@ -24,6 +24,7 @@ declare(strict_types=1);
 namespace FireflyIII\Api\V1\Requests\Models\Rule;
 
 use FireflyIII\Rules\IsBoolean;
+use FireflyIII\Rules\IsValidActionExpression;
 use FireflyIII\Support\Request\ChecksLogin;
 use FireflyIII\Support\Request\ConvertsDataTypes;
 use FireflyIII\Support\Request\GetRuleConfiguration;
@@ -123,7 +124,7 @@ class StoreRequest extends FormRequest
             'triggers.*.stop_processing' => [new IsBoolean()],
             'triggers.*.active'          => [new IsBoolean()],
             'actions.*.type'             => 'required|in:'.implode(',', $validActions),
-            'actions.*.value'            => 'required_if:actions.*.type,'.$contextActions.'|ruleActionValue',
+            'actions.*.value'            => ['required_if:actions.*.type,'.$contextActions, new IsValidActionExpression(), 'ruleActionValue'],
             'actions.*.stop_processing'  => [new IsBoolean()],
             'actions.*.active'           => [new IsBoolean()],
             'strict'                     => [new IsBoolean()],
diff --git a/app/Api/V1/Requests/Models/Rule/UpdateRequest.php b/app/Api/V1/Requests/Models/Rule/UpdateRequest.php
index 3e89716d7f..2d7488b505 100644
--- a/app/Api/V1/Requests/Models/Rule/UpdateRequest.php
+++ b/app/Api/V1/Requests/Models/Rule/UpdateRequest.php
@@ -25,6 +25,7 @@ namespace FireflyIII\Api\V1\Requests\Models\Rule;
 
 use FireflyIII\Models\Rule;
 use FireflyIII\Rules\IsBoolean;
+use FireflyIII\Rules\IsValidActionExpression;
 use FireflyIII\Support\Request\ChecksLogin;
 use FireflyIII\Support\Request\ConvertsDataTypes;
 use FireflyIII\Support\Request\GetRuleConfiguration;
@@ -140,7 +141,7 @@ class UpdateRequest extends FormRequest
             'triggers.*.stop_processing' => [new IsBoolean()],
             'triggers.*.active'          => [new IsBoolean()],
             'actions.*.type'             => 'required|in:'.implode(',', $validActions),
-            'actions.*.value'            => 'required_if:actions.*.type,'.$contextActions.'|ruleActionValue',
+            'actions.*.value'            => ['required_if:actions.*.type,'.$contextActions, new IsValidActionExpression(), 'ruleActionValue'],
             'actions.*.stop_processing'  => [new IsBoolean()],
             'actions.*.active'           => [new IsBoolean()],
             'strict'                     => [new IsBoolean()],
diff --git a/app/Api/V1/Requests/Models/Rule/ValidateExpressionRequest.php b/app/Api/V1/Requests/Models/Rule/ValidateExpressionRequest.php
new file mode 100644
index 0000000000..b0ef5a3998
--- /dev/null
+++ b/app/Api/V1/Requests/Models/Rule/ValidateExpressionRequest.php
@@ -0,0 +1,65 @@
+<?php
+
+/**
+ * ValidateExpressionRequest.php
+ * Copyright (c) 2024 Michael Thomas
+ *
+ * This file is part of Firefly III (https://github.com/firefly-iii).
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+namespace FireflyIII\Api\V1\Requests\Models\Rule;
+
+use FireflyIII\Rules\IsValidActionExpression;
+use FireflyIII\Support\Request\ChecksLogin;
+use Illuminate\Contracts\Validation\Validator;
+use Illuminate\Foundation\Http\FormRequest;
+use Illuminate\Validation\ValidationException;
+
+/**
+ * Class ValidateExpressionRequest
+ */
+class ValidateExpressionRequest extends FormRequest
+{
+    use ChecksLogin;
+
+    public function rules(): array
+    {
+        return ['expression' => ['required', new IsValidActionExpression()]];
+    }
+
+    /**
+     * Handle a failed validation attempt.
+     *
+     * @param  \Illuminate\Contracts\Validation\Validator  $validator
+     * @return void
+     *
+     * @throws \Illuminate\Validation\ValidationException
+     */
+    protected function failedValidation(Validator $validator): void
+    {
+        $error = $validator->errors()->first('expression');
+
+        throw new ValidationException(
+            $validator,
+            response()->json([
+                'valid' => false,
+                'error' => $error
+            ], 200)
+        );
+    }
+}
diff --git a/app/Http/Requests/RuleFormRequest.php b/app/Http/Requests/RuleFormRequest.php
index 6d6f831815..29c2352a56 100644
--- a/app/Http/Requests/RuleFormRequest.php
+++ b/app/Http/Requests/RuleFormRequest.php
@@ -24,6 +24,7 @@ declare(strict_types=1);
 namespace FireflyIII\Http\Requests;
 
 use FireflyIII\Models\Rule;
+use FireflyIII\Rules\IsValidActionExpression;
 use FireflyIII\Support\Request\ChecksLogin;
 use FireflyIII\Support\Request\ConvertsDataTypes;
 use FireflyIII\Support\Request\GetRuleConfiguration;
@@ -147,7 +148,7 @@ class RuleFormRequest extends FormRequest
             'triggers.*.type'  => 'required|in:'.implode(',', $validTriggers),
             'triggers.*.value' => sprintf('required_if:triggers.*.type,%s|max:1024|min:1|ruleTriggerValue', $contextTriggers),
             'actions.*.type'   => 'required|in:'.implode(',', $validActions),
-            'actions.*.value'  => sprintf('required_if:actions.*.type,%s|min:0|max:1024|ruleActionValue', $contextActions),
+            'actions.*.value'  => [sprintf('required_if:actions.*.type,%s|min:0|max:1024', $contextActions), new IsValidActionExpression(), 'ruleActionValue'],
             'strict'           => 'in:0,1',
         ];
 
diff --git a/app/Models/RuleAction.php b/app/Models/RuleAction.php
index f8f8e5fe12..a6f8d44c71 100644
--- a/app/Models/RuleAction.php
+++ b/app/Models/RuleAction.php
@@ -26,6 +26,7 @@ namespace FireflyIII\Models;
 use Carbon\Carbon;
 use Eloquent;
 use FireflyIII\Support\Models\ReturnsIntegerIdTrait;
+use FireflyIII\TransactionRules\Expressions\ActionExpression;
 use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Eloquent\Casts\Attribute;
 use Illuminate\Database\Eloquent\Model;
@@ -93,4 +94,10 @@ class RuleAction extends Model
             get: static fn ($value) => (int)$value,
         );
     }
+
+    public function getValue(array $journal): string
+    {
+        $expr = new ActionExpression($this->action_value);
+        return $expr->evaluate($journal);
+    }
 }
diff --git a/app/Providers/FireflyServiceProvider.php b/app/Providers/FireflyServiceProvider.php
index 3f304c33da..ff7a4f6d30 100644
--- a/app/Providers/FireflyServiceProvider.php
+++ b/app/Providers/FireflyServiceProvider.php
@@ -69,9 +69,11 @@ use FireflyIII\Support\Preferences;
 use FireflyIII\Support\Steam;
 use FireflyIII\TransactionRules\Engine\RuleEngineInterface;
 use FireflyIII\TransactionRules\Engine\SearchRuleEngine;
+use FireflyIII\TransactionRules\Expressions\ActionExpressionLanguageProvider;
 use FireflyIII\Validation\FireflyValidator;
 use Illuminate\Foundation\Application;
 use Illuminate\Support\ServiceProvider;
+use Symfony\Component\ExpressionLanguage\ExpressionLanguage;
 
 /**
  * Class FireflyServiceProvider.
@@ -200,6 +202,16 @@ class FireflyServiceProvider extends ServiceProvider
             }
         );
 
+        // rule expression language
+        $this->app->singleton(
+            ExpressionLanguage::class,
+            static function () {
+                $expressionLanguage = new ExpressionLanguage();
+                $expressionLanguage->registerProvider(new ActionExpressionLanguageProvider());
+                return $expressionLanguage;
+            }
+        );
+
         $this->app->bind(
             RuleEngineInterface::class,
             static function (Application $app) {
diff --git a/app/Rules/IsValidActionExpression.php b/app/Rules/IsValidActionExpression.php
new file mode 100644
index 0000000000..3022043fa7
--- /dev/null
+++ b/app/Rules/IsValidActionExpression.php
@@ -0,0 +1,52 @@
+<?php
+
+/*
+ *
+ * IsValidActionExpression.php
+ * Copyright (c) 2024 Michael Thomas
+ *
+ * This file is part of Firefly III (https://github.com/firefly-iii).
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+namespace FireflyIII\Rules;
+
+use Closure;
+use Illuminate\Contracts\Validation\ValidationRule;
+use FireflyIII\TransactionRules\Expressions\ActionExpression;
+
+class IsValidActionExpression implements ValidationRule
+{
+    /**
+     * Check that the given action expression is syntactically valid.
+     *
+     * @param  \Closure(string): \Illuminate\Translation\PotentiallyTranslatedString  $fail
+     *
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function validate(string $attribute, mixed $value, Closure $fail): void
+    {
+        $value ??= '';
+        $expr = new ActionExpression($value);
+
+        if (!$expr->isValid()) {
+            $fail('validation.rule_action_expression')->translate([
+                'error' => $expr->getValidationError()->getMessage()
+            ]);
+        }
+    }
+}
diff --git a/app/TransactionRules/Actions/AddTag.php b/app/TransactionRules/Actions/AddTag.php
index e9a0ed716d..3381c86277 100644
--- a/app/TransactionRules/Actions/AddTag.php
+++ b/app/TransactionRules/Actions/AddTag.php
@@ -54,11 +54,12 @@ class AddTag implements ActionInterface
         /** @var User $user */
         $user    = User::find($journal['user_id']);
         $factory->setUser($user);
-        $tag     = $factory->findOrCreate($this->action->action_value);
+        $tagName = $this->action->getValue($journal);
+        $tag     = $factory->findOrCreate($tagName);
 
         if (null === $tag) {
             // could not find, could not create tag.
-            event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.find_or_create_tag_failed', ['tag' => $this->action->action_value])));
+            event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.find_or_create_tag_failed', ['tag' => $tagName])));
 
             return false;
         }
@@ -84,7 +85,7 @@ class AddTag implements ActionInterface
         app('log')->debug(
             sprintf('RuleAction AddTag fired but tag %d ("%s") was already added to journal %d.', $tag->id, $tag->tag, $journal['transaction_journal_id'])
         );
-        event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.tag_already_added', ['tag' => $this->action->action_value])));
+        event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.tag_already_added', ['tag' => $tagName])));
 
         return false;
     }
diff --git a/app/TransactionRules/Actions/AppendDescription.php b/app/TransactionRules/Actions/AppendDescription.php
index 5b5b318ce0..42d6c58151 100644
--- a/app/TransactionRules/Actions/AppendDescription.php
+++ b/app/TransactionRules/Actions/AppendDescription.php
@@ -44,7 +44,8 @@ class AppendDescription implements ActionInterface
 
     public function actOnArray(array $journal): bool
     {
-        $description = sprintf('%s %s', $journal['description'], $this->action->action_value);
+        $append      = $this->action->getValue($journal);
+        $description = sprintf('%s %s', $journal['description'], $append);
         \DB::table('transaction_journals')->where('id', $journal['transaction_journal_id'])->limit(1)->update(['description' => $description]);
 
         // event for audit log entry
diff --git a/app/TransactionRules/Actions/AppendNotes.php b/app/TransactionRules/Actions/AppendNotes.php
index bb990d438f..e584a48251 100644
--- a/app/TransactionRules/Actions/AppendNotes.php
+++ b/app/TransactionRules/Actions/AppendNotes.php
@@ -55,15 +55,16 @@ class AppendNotes implements ActionInterface
             $dbNote->noteable_type = TransactionJournal::class;
             $dbNote->text          = '';
         }
-        app('log')->debug(sprintf('RuleAction AppendNotes appended "%s" to "%s".', $this->action->action_value, $dbNote->text));
         $before       = $dbNote->text;
-        $text         = sprintf('%s%s', $dbNote->text, $this->action->action_value);
+        $append       = $this->action->getValue($journal);
+        $text         = sprintf('%s%s', $dbNote->text, $append);
         $dbNote->text = $text;
         $dbNote->save();
 
         /** @var TransactionJournal $object */
         $object       = TransactionJournal::where('user_id', $journal['user_id'])->find($journal['transaction_journal_id']);
 
+        app('log')->debug(sprintf('RuleAction AppendNotes appended "%s" to "%s".', $append, $before));
         event(new TriggeredAuditLog($this->action->rule, $object, 'update_notes', $before, $text));
 
         return true;
diff --git a/app/TransactionRules/Actions/ConvertToDeposit.php b/app/TransactionRules/Actions/ConvertToDeposit.php
index e8f9abf59e..942df9f6a6 100644
--- a/app/TransactionRules/Actions/ConvertToDeposit.php
+++ b/app/TransactionRules/Actions/ConvertToDeposit.php
@@ -52,16 +52,18 @@ class ConvertToDeposit implements ActionInterface
 
     public function actOnArray(array $journal): bool
     {
+        $actionValue = $this->action->getValue($journal);
+
         // make object from array (so the data is fresh).
         /** @var null|TransactionJournal $object */
-        $object     = TransactionJournal::where('user_id', $journal['user_id'])->find($journal['transaction_journal_id']);
+        $object      = TransactionJournal::where('user_id', $journal['user_id'])->find($journal['transaction_journal_id']);
         if (null === $object) {
             app('log')->error(sprintf('Cannot find journal #%d, cannot convert to deposit.', $journal['transaction_journal_id']));
             event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.journal_not_found')));
 
             return false;
         }
-        $groupCount = TransactionJournal::where('transaction_group_id', $journal['transaction_group_id'])->count();
+        $groupCount  = TransactionJournal::where('transaction_group_id', $journal['transaction_group_id'])->count();
         if ($groupCount > 1) {
             app('log')->error(sprintf('Group #%d has more than one transaction in it, cannot convert to deposit.', $journal['transaction_group_id']));
             event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.split_group')));
@@ -70,7 +72,7 @@ class ConvertToDeposit implements ActionInterface
         }
 
         app('log')->debug(sprintf('Convert journal #%d to deposit.', $journal['transaction_journal_id']));
-        $type       = $object->transactionType->type;
+        $type        = $object->transactionType->type;
         if (TransactionType::DEPOSIT === $type) {
             app('log')->error(sprintf('Journal #%d is already a deposit (rule #%d).', $journal['transaction_journal_id'], $this->action->rule_id));
             event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.is_already_deposit')));
@@ -82,7 +84,7 @@ class ConvertToDeposit implements ActionInterface
             app('log')->debug('Going to transform a withdrawal to a deposit.');
 
             try {
-                $res = $this->convertWithdrawalArray($object);
+                $res = $this->convertWithdrawalArray($object, $actionValue);
             } catch (FireflyException $e) {
                 app('log')->debug('Could not convert withdrawal to deposit.');
                 app('log')->error($e->getMessage());
@@ -99,7 +101,7 @@ class ConvertToDeposit implements ActionInterface
             app('log')->debug('Going to transform a transfer to a deposit.');
 
             try {
-                $res = $this->convertTransferArray($object);
+                $res = $this->convertTransferArray($object, $actionValue);
             } catch (FireflyException $e) {
                 app('log')->debug('Could not convert transfer to deposit.');
                 app('log')->error($e->getMessage());
@@ -122,7 +124,7 @@ class ConvertToDeposit implements ActionInterface
      *
      * @throws FireflyException
      */
-    private function convertWithdrawalArray(TransactionJournal $journal): bool
+    private function convertWithdrawalArray(TransactionJournal $journal, string $actionValue = ''): bool
     {
         $user            = $journal->user;
 
@@ -139,7 +141,7 @@ class ConvertToDeposit implements ActionInterface
 
         // get the action value, or use the original destination name in case the action value is empty:
         // this becomes a new or existing (revenue) account, which is the source of the new deposit.
-        $opposingName    = '' === $this->action->action_value ? $destAccount->name : $this->action->action_value;
+        $opposingName    = '' === $actionValue ? $destAccount->name : $actionValue;
         // we check all possible source account types if one exists:
         $validTypes      = config('firefly.expected_source_types.source.Deposit');
         $opposingAccount = $repository->findByName($opposingName, $validTypes);
@@ -147,7 +149,7 @@ class ConvertToDeposit implements ActionInterface
             $opposingAccount = $factory->findOrCreate($opposingName, AccountType::REVENUE);
         }
 
-        app('log')->debug(sprintf('ConvertToDeposit. Action value is "%s", new opposing name is "%s"', $this->action->action_value, $opposingAccount->name));
+        app('log')->debug(sprintf('ConvertToDeposit. Action value is "%s", new opposing name is "%s"', $actionValue, $opposingAccount->name));
 
         // update the source transaction and put in the new revenue ID.
         \DB::table('transactions')
@@ -211,7 +213,7 @@ class ConvertToDeposit implements ActionInterface
      *
      * @throws FireflyException
      */
-    private function convertTransferArray(TransactionJournal $journal): bool
+    private function convertTransferArray(TransactionJournal $journal, string $actionValue = ''): bool
     {
         $user            = $journal->user;
 
@@ -227,7 +229,7 @@ class ConvertToDeposit implements ActionInterface
 
         // get the action value, or use the original source name in case the action value is empty:
         // this becomes a new or existing (revenue) account, which is the source of the new deposit.
-        $opposingName    = '' === $this->action->action_value ? $sourceAccount->name : $this->action->action_value;
+        $opposingName    = '' === $actionValue ? $sourceAccount->name : $actionValue;
         // we check all possible source account types if one exists:
         $validTypes      = config('firefly.expected_source_types.source.Deposit');
         $opposingAccount = $repository->findByName($opposingName, $validTypes);
@@ -235,7 +237,7 @@ class ConvertToDeposit implements ActionInterface
             $opposingAccount = $factory->findOrCreate($opposingName, AccountType::REVENUE);
         }
 
-        app('log')->debug(sprintf('ConvertToDeposit. Action value is "%s", revenue name is "%s"', $this->action->action_value, $opposingAccount->name));
+        app('log')->debug(sprintf('ConvertToDeposit. Action value is "%s", revenue name is "%s"', $actionValue, $opposingAccount->name));
 
         // update source transaction(s) to be revenue account
         \DB::table('transactions')
diff --git a/app/TransactionRules/Actions/ConvertToTransfer.php b/app/TransactionRules/Actions/ConvertToTransfer.php
index 323270f35c..f2a0438f74 100644
--- a/app/TransactionRules/Actions/ConvertToTransfer.php
+++ b/app/TransactionRules/Actions/ConvertToTransfer.php
@@ -55,6 +55,8 @@ class ConvertToTransfer implements ActionInterface
      */
     public function actOnArray(array $journal): bool
     {
+        $accountName  = $this->action->getValue($journal);
+
         // make object from array (so the data is fresh).
         /** @var null|TransactionJournal $object */
         $object       = TransactionJournal::where('user_id', $journal['user_id'])->find($journal['transaction_journal_id']);
@@ -102,7 +104,7 @@ class ConvertToTransfer implements ActionInterface
             $expectedType = $this->getDestinationType($journalId);
             // Deposit? Replace source with account with same type as destination.
         }
-        $opposing     = $repository->findByName($this->action->action_value, [$expectedType]);
+        $opposing     = $repository->findByName($accountName, [$expectedType]);
 
         if (null === $opposing) {
             app('log')->error(
@@ -110,11 +112,11 @@ class ConvertToTransfer implements ActionInterface
                     'Journal #%d cannot be converted because no valid %s account with name "%s" exists (rule #%d).',
                     $expectedType,
                     $journalId,
-                    $this->action->action_value,
+                    $accountName,
                     $this->action->rule_id
                 )
             );
-            event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.no_valid_opposing', ['name' => $this->action->action_value])));
+            event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.no_valid_opposing', ['name' => $accountName])));
 
             return false;
         }
diff --git a/app/TransactionRules/Actions/ConvertToWithdrawal.php b/app/TransactionRules/Actions/ConvertToWithdrawal.php
index d7b9684826..79c18a0333 100644
--- a/app/TransactionRules/Actions/ConvertToWithdrawal.php
+++ b/app/TransactionRules/Actions/ConvertToWithdrawal.php
@@ -52,16 +52,18 @@ class ConvertToWithdrawal implements ActionInterface
 
     public function actOnArray(array $journal): bool
     {
+        $actionValue = $this->action->getValue($journal);
+
         // make object from array (so the data is fresh).
         /** @var null|TransactionJournal $object */
-        $object     = TransactionJournal::where('user_id', $journal['user_id'])->find($journal['transaction_journal_id']);
+        $object      = TransactionJournal::where('user_id', $journal['user_id'])->find($journal['transaction_journal_id']);
         if (null === $object) {
             app('log')->error(sprintf('Cannot find journal #%d, cannot convert to withdrawal.', $journal['transaction_journal_id']));
             event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.journal_not_found')));
 
             return false;
         }
-        $groupCount = TransactionJournal::where('transaction_group_id', $journal['transaction_group_id'])->count();
+        $groupCount  = TransactionJournal::where('transaction_group_id', $journal['transaction_group_id'])->count();
         if ($groupCount > 1) {
             app('log')->error(sprintf('Group #%d has more than one transaction in it, cannot convert to withdrawal.', $journal['transaction_group_id']));
             event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.split_group')));
@@ -69,7 +71,7 @@ class ConvertToWithdrawal implements ActionInterface
             return false;
         }
 
-        $type       = $object->transactionType->type;
+        $type        = $object->transactionType->type;
         if (TransactionType::WITHDRAWAL === $type) {
             app('log')->error(sprintf('Journal #%d is already a withdrawal (rule #%d).', $journal['transaction_journal_id'], $this->action->rule_id));
             event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.is_already_withdrawal')));
@@ -85,7 +87,7 @@ class ConvertToWithdrawal implements ActionInterface
             app('log')->debug('Going to transform a deposit to a withdrawal.');
 
             try {
-                $res = $this->convertDepositArray($object);
+                $res = $this->convertDepositArray($object, $actionValue);
             } catch (FireflyException $e) {
                 app('log')->debug('Could not convert transfer to deposit.');
                 app('log')->error($e->getMessage());
@@ -101,7 +103,7 @@ class ConvertToWithdrawal implements ActionInterface
         app('log')->debug('Going to transform a transfer to a withdrawal.');
 
         try {
-            $res = $this->convertTransferArray($object);
+            $res = $this->convertTransferArray($object, $actionValue);
         } catch (FireflyException $e) {
             app('log')->debug('Could not convert transfer to deposit.');
             app('log')->error($e->getMessage());
@@ -117,7 +119,7 @@ class ConvertToWithdrawal implements ActionInterface
     /**
      * @throws FireflyException
      */
-    private function convertDepositArray(TransactionJournal $journal): bool
+    private function convertDepositArray(TransactionJournal $journal, string $actionValue = ''): bool
     {
         $user            = $journal->user;
 
@@ -133,7 +135,7 @@ class ConvertToWithdrawal implements ActionInterface
 
         // get the action value, or use the original source name in case the action value is empty:
         // this becomes a new or existing (expense) account, which is the destination of the new withdrawal.
-        $opposingName    = '' === $this->action->action_value ? $sourceAccount->name : $this->action->action_value;
+        $opposingName    = '' === $actionValue ? $sourceAccount->name : $actionValue;
         // we check all possible source account types if one exists:
         $validTypes      = config('firefly.expected_source_types.destination.Withdrawal');
         $opposingAccount = $repository->findByName($opposingName, $validTypes);
@@ -141,7 +143,7 @@ class ConvertToWithdrawal implements ActionInterface
             $opposingAccount = $factory->findOrCreate($opposingName, AccountType::EXPENSE);
         }
 
-        app('log')->debug(sprintf('ConvertToWithdrawal. Action value is "%s", expense name is "%s"', $this->action->action_value, $opposingName));
+        app('log')->debug(sprintf('ConvertToWithdrawal. Action value is "%s", expense name is "%s"', $actionValue, $opposingName));
 
         // update source transaction(s) to be the original destination account
         \DB::table('transactions')
@@ -203,7 +205,7 @@ class ConvertToWithdrawal implements ActionInterface
      *
      * @throws FireflyException
      */
-    private function convertTransferArray(TransactionJournal $journal): bool
+    private function convertTransferArray(TransactionJournal $journal, string $actionValue = ''): bool
     {
         // find or create expense account.
         $user            = $journal->user;
@@ -219,7 +221,7 @@ class ConvertToWithdrawal implements ActionInterface
 
         // get the action value, or use the original source name in case the action value is empty:
         // this becomes a new or existing (expense) account, which is the destination of the new withdrawal.
-        $opposingName    = '' === $this->action->action_value ? $destAccount->name : $this->action->action_value;
+        $opposingName    = '' === $actionValue ? $destAccount->name : $actionValue;
         // we check all possible source account types if one exists:
         $validTypes      = config('firefly.expected_source_types.destination.Withdrawal');
         $opposingAccount = $repository->findByName($opposingName, $validTypes);
@@ -227,7 +229,7 @@ class ConvertToWithdrawal implements ActionInterface
             $opposingAccount = $factory->findOrCreate($opposingName, AccountType::EXPENSE);
         }
 
-        app('log')->debug(sprintf('ConvertToWithdrawal. Action value is "%s", destination name is "%s"', $this->action->action_value, $opposingName));
+        app('log')->debug(sprintf('ConvertToWithdrawal. Action value is "%s", destination name is "%s"', $actionValue, $opposingName));
 
         // update destination transaction(s) to be new expense account.
         \DB::table('transactions')
diff --git a/app/TransactionRules/Actions/LinkToBill.php b/app/TransactionRules/Actions/LinkToBill.php
index f9e0406d34..a073c657e1 100644
--- a/app/TransactionRules/Actions/LinkToBill.php
+++ b/app/TransactionRules/Actions/LinkToBill.php
@@ -54,7 +54,7 @@ class LinkToBill implements ActionInterface
         /** @var BillRepositoryInterface $repository */
         $repository = app(BillRepositoryInterface::class);
         $repository->setUser($user);
-        $billName   = (string)$this->action->action_value;
+        $billName   = $this->action->getValue($journal);
         $bill       = $repository->findByName($billName);
 
         if (null !== $bill && TransactionType::WITHDRAWAL === $journal['transaction_type_type']) {
diff --git a/app/TransactionRules/Actions/PrependDescription.php b/app/TransactionRules/Actions/PrependDescription.php
index f00db5d501..47fda2aab5 100644
--- a/app/TransactionRules/Actions/PrependDescription.php
+++ b/app/TransactionRules/Actions/PrependDescription.php
@@ -45,7 +45,7 @@ class PrependDescription implements ActionInterface
     public function actOnArray(array $journal): bool
     {
         $before = $journal['description'];
-        $after  = sprintf('%s%s', $this->action->action_value, $journal['description']);
+        $after  = sprintf('%s%s', $this->action->getValue($journal), $journal['description']);
         \DB::table('transaction_journals')->where('id', $journal['transaction_journal_id'])->limit(1)->update(['description' => $after]);
 
         // journal
diff --git a/app/TransactionRules/Actions/PrependNotes.php b/app/TransactionRules/Actions/PrependNotes.php
index 7bbfd70f71..31e455a38b 100644
--- a/app/TransactionRules/Actions/PrependNotes.php
+++ b/app/TransactionRules/Actions/PrependNotes.php
@@ -56,8 +56,9 @@ class PrependNotes implements ActionInterface
             $dbNote->text          = '';
         }
         $before       = $dbNote->text;
-        app('log')->debug(sprintf('RuleAction PrependNotes prepended "%s" to "%s".', $this->action->action_value, $dbNote->text));
-        $text         = sprintf('%s%s', $this->action->action_value, $dbNote->text);
+        $after        = $this->action->getValue($journal);
+        app('log')->debug(sprintf('RuleAction PrependNotes prepended "%s" to "%s".', $after, $dbNote->text));
+        $text         = sprintf('%s%s', $after, $dbNote->text);
         $dbNote->text = $text;
         $dbNote->save();
 
diff --git a/app/TransactionRules/Actions/RemoveTag.php b/app/TransactionRules/Actions/RemoveTag.php
index 55ef91531a..a717043ce2 100644
--- a/app/TransactionRules/Actions/RemoveTag.php
+++ b/app/TransactionRules/Actions/RemoveTag.php
@@ -46,13 +46,13 @@ class RemoveTag implements ActionInterface
 
     public function actOnArray(array $journal): bool
     {
-        // if tag does not exist, no need to continue:
-        $name   = $this->action->action_value;
+        $name   = $this->action->getValue($journal);
 
         /** @var User $user */
         $user   = User::find($journal['user_id']);
         $tag    = $user->tags()->where('tag', $name)->first();
 
+        // if tag does not exist, no need to continue:
         if (null === $tag) {
             app('log')->debug(
                 sprintf('RuleAction RemoveTag tried to remove tag "%s" from journal #%d but no such tag exists.', $name, $journal['transaction_journal_id'])
diff --git a/app/TransactionRules/Actions/SetBudget.php b/app/TransactionRules/Actions/SetBudget.php
index 260ea63cb5..067dc93a49 100644
--- a/app/TransactionRules/Actions/SetBudget.php
+++ b/app/TransactionRules/Actions/SetBudget.php
@@ -49,7 +49,7 @@ class SetBudget implements ActionInterface
     {
         /** @var User $user */
         $user          = User::find($journal['user_id']);
-        $search        = $this->action->action_value;
+        $search        = $this->action->getValue($journal);
 
         $budget        = $user->budgets()->where('name', $search)->first();
         if (null === $budget) {
diff --git a/app/TransactionRules/Actions/SetCategory.php b/app/TransactionRules/Actions/SetCategory.php
index 8785ade043..760f0e01d5 100644
--- a/app/TransactionRules/Actions/SetCategory.php
+++ b/app/TransactionRules/Actions/SetCategory.php
@@ -49,7 +49,7 @@ class SetCategory implements ActionInterface
     {
         /** @var null|User $user */
         $user            = User::find($journal['user_id']);
-        $search          = $this->action->action_value;
+        $search          = $this->action->getValue($journal);
         if (null === $user) {
             app('log')->error(sprintf('Journal has no valid user ID so action SetCategory("%s") cannot be applied', $search), $journal);
             event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.no_such_journal')));
diff --git a/app/TransactionRules/Actions/SetDescription.php b/app/TransactionRules/Actions/SetDescription.php
index 3d5e392014..f423806e5e 100644
--- a/app/TransactionRules/Actions/SetDescription.php
+++ b/app/TransactionRules/Actions/SetDescription.php
@@ -47,10 +47,11 @@ class SetDescription implements ActionInterface
         /** @var TransactionJournal $object */
         $object = TransactionJournal::where('user_id', $journal['user_id'])->find($journal['transaction_journal_id']);
         $before = $object->description;
+        $after  = $this->action->getValue($journal);
 
         \DB::table('transaction_journals')
             ->where('id', '=', $journal['transaction_journal_id'])
-            ->update(['description' => $this->action->action_value])
+            ->update(['description' => $after])
         ;
 
         app('log')->debug(
@@ -58,11 +59,11 @@ class SetDescription implements ActionInterface
                 'RuleAction SetDescription changed the description of journal #%d from "%s" to "%s".',
                 $journal['transaction_journal_id'],
                 $journal['description'],
-                $this->action->action_value
+                $after
             )
         );
         $object->refresh();
-        event(new TriggeredAuditLog($this->action->rule, $object, 'update_description', $before, $this->action->action_value));
+        event(new TriggeredAuditLog($this->action->rule, $object, 'update_description', $before, $after));
 
         return true;
     }
diff --git a/app/TransactionRules/Actions/SetDestinationAccount.php b/app/TransactionRules/Actions/SetDestinationAccount.php
index 455acb4dfd..4b8498de8d 100644
--- a/app/TransactionRules/Actions/SetDestinationAccount.php
+++ b/app/TransactionRules/Actions/SetDestinationAccount.php
@@ -51,6 +51,8 @@ class SetDestinationAccount implements ActionInterface
 
     public function actOnArray(array $journal): bool
     {
+        $accountName      = $this->action->getValue($journal);
+
         /** @var User $user */
         $user             = User::find($journal['user_id']);
 
@@ -68,16 +70,16 @@ class SetDestinationAccount implements ActionInterface
         $this->repository->setUser($user);
 
         // if this is a transfer or a deposit, the new destination account must be an asset account or a default account, and it MUST exist:
-        $newAccount       = $this->findAssetAccount($type);
+        $newAccount       = $this->findAssetAccount($type, $accountName);
         if ((TransactionType::DEPOSIT === $type || TransactionType::TRANSFER === $type) && null === $newAccount) {
             app('log')->error(
                 sprintf(
                     'Cant change destination account of journal #%d because no asset account with name "%s" exists.',
                     $object->id,
-                    $this->action->action_value
+                    $accountName
                 )
             );
-            event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.cannot_find_asset', ['name' => $this->action->action_value])));
+            event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.cannot_find_asset', ['name' => $accountName])));
 
             return false;
         }
@@ -115,7 +117,7 @@ class SetDestinationAccount implements ActionInterface
         // if this is a withdrawal, the new destination account must be a expense account and may be created:
         // or it is a liability, in which case it must be returned.
         if (TransactionType::WITHDRAWAL === $type) {
-            $newAccount = $this->findWithdrawalDestinationAccount();
+            $newAccount = $this->findWithdrawalDestinationAccount($accountName);
         }
 
         app('log')->debug(sprintf('New destination account is #%d ("%s").', $newAccount->id, $newAccount->name));
@@ -134,23 +136,23 @@ class SetDestinationAccount implements ActionInterface
         return true;
     }
 
-    private function findAssetAccount(string $type): ?Account
+    private function findAssetAccount(string $type, string $accountName): ?Account
     {
         // switch on type:
         $allowed = config(sprintf('firefly.expected_source_types.destination.%s', $type));
         $allowed = is_array($allowed) ? $allowed : [];
         app('log')->debug(sprintf('Check config for expected_source_types.destination.%s, result is', $type), $allowed);
 
-        return $this->repository->findByName($this->action->action_value, $allowed);
+        return $this->repository->findByName($accountName, $allowed);
     }
 
-    private function findWithdrawalDestinationAccount(): Account
+    private function findWithdrawalDestinationAccount(string $accountName): Account
     {
         $allowed = config('firefly.expected_source_types.destination.Withdrawal');
-        $account = $this->repository->findByName($this->action->action_value, $allowed);
+        $account = $this->repository->findByName($accountName, $allowed);
         if (null === $account) {
             $data    = [
-                'name'              => $this->action->action_value,
+                'name'              => $accountName,
                 'account_type_name' => 'expense',
                 'account_type_id'   => null,
                 'virtual_balance'   => 0,
diff --git a/app/TransactionRules/Actions/SetNotes.php b/app/TransactionRules/Actions/SetNotes.php
index 260ccfe4d4..e8e3e92f2c 100644
--- a/app/TransactionRules/Actions/SetNotes.php
+++ b/app/TransactionRules/Actions/SetNotes.php
@@ -55,7 +55,8 @@ class SetNotes implements ActionInterface
             $dbNote->text          = '';
         }
         $oldNotes     = $dbNote->text;
-        $dbNote->text = $this->action->action_value;
+        $newNotes     = $this->action->getValue($journal);
+        $dbNote->text = $newNotes;
         $dbNote->save();
 
         app('log')->debug(
@@ -63,14 +64,14 @@ class SetNotes implements ActionInterface
                 'RuleAction SetNotes changed the notes of journal #%d from "%s" to "%s".',
                 $journal['transaction_journal_id'],
                 $oldNotes,
-                $this->action->action_value
+                $newNotes
             )
         );
 
         /** @var TransactionJournal $object */
         $object       = TransactionJournal::where('user_id', $journal['user_id'])->find($journal['transaction_journal_id']);
 
-        event(new TriggeredAuditLog($this->action->rule, $object, 'update_notes', $oldNotes, $this->action->action_value));
+        event(new TriggeredAuditLog($this->action->rule, $object, 'update_notes', $oldNotes, $newNotes));
 
         return true;
     }
diff --git a/app/TransactionRules/Actions/SetSourceAccount.php b/app/TransactionRules/Actions/SetSourceAccount.php
index aafe75569b..9da778d2a6 100644
--- a/app/TransactionRules/Actions/SetSourceAccount.php
+++ b/app/TransactionRules/Actions/SetSourceAccount.php
@@ -51,6 +51,8 @@ class SetSourceAccount implements ActionInterface
 
     public function actOnArray(array $journal): bool
     {
+        $accountName      = $this->action->getValue($journal);
+
         /** @var User $user */
         $user             = User::find($journal['user_id']);
 
@@ -67,12 +69,12 @@ class SetSourceAccount implements ActionInterface
         $this->repository->setUser($user);
 
         // if this is a transfer or a withdrawal, the new source account must be an asset account or a default account, and it MUST exist:
-        $newAccount       = $this->findAssetAccount($type);
+        $newAccount       = $this->findAssetAccount($type, $accountName);
         if ((TransactionType::WITHDRAWAL === $type || TransactionType::TRANSFER === $type) && null === $newAccount) {
             app('log')->error(
-                sprintf('Cant change source account of journal #%d because no asset account with name "%s" exists.', $object->id, $this->action->action_value)
+                sprintf('Cant change source account of journal #%d because no asset account with name "%s" exists.', $object->id, $accountName)
             );
-            event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.cannot_find_asset', ['name' => $this->action->action_value])));
+            event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.cannot_find_asset', ['name' => $accountName])));
 
             return false;
         }
@@ -109,7 +111,7 @@ class SetSourceAccount implements ActionInterface
         // if this is a deposit, the new source account must be a revenue account and may be created:
         // or it's a liability
         if (TransactionType::DEPOSIT === $type) {
-            $newAccount = $this->findDepositSourceAccount();
+            $newAccount = $this->findDepositSourceAccount($accountName);
         }
 
         app('log')->debug(sprintf('New source account is #%d ("%s").', $newAccount->id, $newAccount->name));
@@ -128,24 +130,24 @@ class SetSourceAccount implements ActionInterface
         return true;
     }
 
-    private function findAssetAccount(string $type): ?Account
+    private function findAssetAccount(string $type, string $accountName): ?Account
     {
         // switch on type:
         $allowed = config(sprintf('firefly.expected_source_types.source.%s', $type));
         $allowed = is_array($allowed) ? $allowed : [];
         app('log')->debug(sprintf('Check config for expected_source_types.source.%s, result is', $type), $allowed);
 
-        return $this->repository->findByName($this->action->action_value, $allowed);
+        return $this->repository->findByName($accountName, $allowed);
     }
 
-    private function findDepositSourceAccount(): Account
+    private function findDepositSourceAccount(string $accountName): Account
     {
         $allowed = config('firefly.expected_source_types.source.Deposit');
-        $account = $this->repository->findByName($this->action->action_value, $allowed);
+        $account = $this->repository->findByName($accountName, $allowed);
         if (null === $account) {
             // create new revenue account with this name:
             $data    = [
-                'name'              => $this->action->action_value,
+                'name'              => $accountName,
                 'account_type_name' => 'revenue',
                 'account_type_id'   => null,
                 'virtual_balance'   => 0,
diff --git a/app/TransactionRules/Actions/UpdatePiggybank.php b/app/TransactionRules/Actions/UpdatePiggybank.php
index 4bd1d1de19..a978ed4946 100644
--- a/app/TransactionRules/Actions/UpdatePiggybank.php
+++ b/app/TransactionRules/Actions/UpdatePiggybank.php
@@ -50,6 +50,8 @@ class UpdatePiggybank implements ActionInterface
 
     public function actOnArray(array $journal): bool
     {
+        $actionValue = $this->action->getValue($journal);
+
         app('log')->debug(sprintf('Triggered rule action UpdatePiggybank on journal #%d', $journal['transaction_journal_id']));
 
         // refresh the transaction type.
@@ -59,12 +61,12 @@ class UpdatePiggybank implements ActionInterface
         /** @var TransactionJournal $journalObj */
         $journalObj  = $user->transactionJournals()->find($journal['transaction_journal_id']);
 
-        $piggyBank   = $this->findPiggyBank($user);
+        $piggyBank   = $this->findPiggyBank($user, $actionValue);
         if (null === $piggyBank) {
             app('log')->info(
-                sprintf('No piggy bank named "%s", cant execute action #%d of rule #%d', $this->action->action_value, $this->action->id, $this->action->rule_id)
+                sprintf('No piggy bank named "%s", cant execute action #%d of rule #%d', $actionValue, $this->action->id, $this->action->rule_id)
             );
-            event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.cannot_find_piggy', ['name' => $this->action->action_value])));
+            event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.cannot_find_piggy', ['name' => $actionValue])));
 
             return false;
         }
@@ -126,14 +128,14 @@ class UpdatePiggybank implements ActionInterface
                 $destination->account_id
             )
         );
-        event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.no_link_piggy', ['name' => $this->action->action_value])));
+        event(new RuleActionFailedOnArray($this->action, $journal, trans('rules.no_link_piggy', ['name' => $actionValue])));
 
         return false;
     }
 
-    private function findPiggyBank(User $user): ?PiggyBank
+    private function findPiggyBank(User $user, string $name): ?PiggyBank
     {
-        return $user->piggyBanks()->where('piggy_banks.name', $this->action->action_value)->first();
+        return $user->piggyBanks()->where('piggy_banks.name', $name)->first();
     }
 
     private function removeAmount(PiggyBank $piggyBank, TransactionJournal $journal, string $amount): void
diff --git a/app/TransactionRules/Expressions/ActionExpression.php b/app/TransactionRules/Expressions/ActionExpression.php
new file mode 100644
index 0000000000..59b9770e14
--- /dev/null
+++ b/app/TransactionRules/Expressions/ActionExpression.php
@@ -0,0 +1,155 @@
+<?php
+
+/**
+ * ActionExpression.php
+ * Copyright (c) 2024 Michael Thomas
+ *
+ * This file is part of Firefly III (https://github.com/firefly-iii).
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+namespace FireflyIII\TransactionRules\Expressions;
+
+use Symfony\Component\ExpressionLanguage\ExpressionLanguage;
+use Symfony\Component\ExpressionLanguage\SyntaxError;
+
+class ActionExpression
+{
+    private static array $NAMES = array(
+        "transaction_group_id",
+        "user_id",
+        "user_group_id",
+        "created_at",
+        "updated_at",
+        "transaction_group_title",
+        "group_created_at",
+        "group_updated_at",
+        "transaction_journal_id",
+        "transaction_type_id",
+        "description",
+        "date",
+        "order",
+        "transaction_type_type",
+        "source_transaction_id",
+        "source_account_id",
+        "reconciled",
+        "amount",
+        "currency_id",
+        "currency_code",
+        "currency_name",
+        "currency_symbol",
+        "currency_decimal_places",
+        "foreign_amount",
+        "foreign_currency_id",
+        "foreign_currency_code",
+        "foreign_currency_name",
+        "foreign_currency_symbol",
+        "foreign_currency_decimal_places",
+        "destination_account_id",
+        "source_account_name",
+        "source_account_iban",
+        "source_account_type",
+        "destination_account_name",
+        "destination_account_iban",
+        "destination_account_type",
+        "category_id",
+        "category_name",
+        "budget_id",
+        "budget_name",
+        "tags",
+        "attachments",
+        "interest_date",
+        "payment_date",
+        "invoice_date",
+        "book_date",
+        "due_date",
+        "process_date",
+        "destination_transaction_id"
+    );
+
+    private ExpressionLanguage $expressionLanguage;
+    private string $expr;
+    private bool $isExpression;
+    private ?SyntaxError $validationError;
+
+    public function __construct(string $expr)
+    {
+        $this->expressionLanguage = app(ExpressionLanguage::class);
+        $this->expr = $expr;
+
+        $this->isExpression = self::isExpression($expr);
+        $this->validationError = $this->validate();
+    }
+
+    private static function isExpression(string $expr): bool
+    {
+        return str_starts_with($expr, "=");
+    }
+
+    private function validate(): ?SyntaxError
+    {
+        if (!$this->isExpression) {
+            return null;
+        }
+
+        try {
+            $this->lint();
+            return null;
+        } catch (SyntaxError $e) {
+            return $e;
+        }
+    }
+
+    private function lintExpression(string $expr): void
+    {
+        $this->expressionLanguage->lint($expr, self::$NAMES);
+    }
+
+    private function lint(): void
+    {
+        if (!$this->isExpression) {
+            return;
+        }
+
+        $this->lintExpression(substr($this->expr, 1));
+    }
+
+    public function isValid(): bool
+    {
+        return $this->validationError === null;
+    }
+
+    public function getValidationError(): ?SyntaxError
+    {
+        return $this->validationError;
+    }
+
+    private function evaluateExpression(string $expr, array $journal): string
+    {
+        $result = $this->expressionLanguage->evaluate($expr, $journal);
+        return strval($result);
+    }
+
+    public function evaluate(array $journal): string
+    {
+        if (!$this->isExpression) {
+            return $this->expr;
+        }
+
+        return $this->evaluateExpression(substr($this->expr, 1), $journal);
+    }
+}
diff --git a/app/TransactionRules/Expressions/ActionExpressionLanguageProvider.php b/app/TransactionRules/Expressions/ActionExpressionLanguageProvider.php
new file mode 100644
index 0000000000..2c54752b00
--- /dev/null
+++ b/app/TransactionRules/Expressions/ActionExpressionLanguageProvider.php
@@ -0,0 +1,39 @@
+<?php
+
+/**
+ * ActionExpressionLanguageProvider.php
+ * Copyright (c) 2024 Michael Thomas
+ *
+ * This file is part of Firefly III (https://github.com/firefly-iii).
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+namespace FireflyIII\TransactionRules\Expressions;
+
+use Symfony\Component\ExpressionLanguage\ExpressionFunction;
+use Symfony\Component\ExpressionLanguage\ExpressionFunctionProviderInterface;
+
+class ActionExpressionLanguageProvider implements ExpressionFunctionProviderInterface
+{
+    public function getFunctions(): array
+    {
+        return [
+            ExpressionFunction::fromPhp("substr"),
+            ExpressionFunction::fromPhp("strlen")
+        ];
+    }
+}
diff --git a/app/Validation/FireflyValidator.php b/app/Validation/FireflyValidator.php
index 891fcc6163..9a554d79b4 100644
--- a/app/Validation/FireflyValidator.php
+++ b/app/Validation/FireflyValidator.php
@@ -35,6 +35,7 @@ use FireflyIII\Repositories\Budget\BudgetRepositoryInterface;
 use FireflyIII\Repositories\PiggyBank\PiggyBankRepositoryInterface;
 use FireflyIII\Services\Password\Verifier;
 use FireflyIII\Support\ParseDateString;
+use FireflyIII\TransactionRules\Expressions\ActionExpression;
 use FireflyIII\User;
 use Illuminate\Validation\Validator;
 use PragmaRX\Google2FA\Exceptions\IncompatibleWithGoogleAuthenticatorException;
@@ -268,6 +269,11 @@ class FireflyValidator extends Validator
             return false;
         }
 
+        // if value is an expression, assume valid
+        if (str_starts_with($value, '=')) {
+            return true;
+        }
+
         // if it's set_budget, verify the budget name:
         if ('set_budget' === $actionType) {
             /** @var BudgetRepositoryInterface $repository */
diff --git a/composer.json b/composer.json
index 8aedc9f70f..5a8d4c7eee 100644
--- a/composer.json
+++ b/composer.json
@@ -105,6 +105,7 @@
         "spatie/laravel-html": "^3.2",
         "spatie/laravel-ignition": "^2",
         "spatie/period": "^2.4",
+        "symfony/expression-language": "^6.4",
         "symfony/http-client": "^7.0",
         "symfony/mailgun-mailer": "^7.0",
         "therobfonz/laravel-mandrill-driver": "^5.0"
@@ -124,8 +125,7 @@
         "phpunit/phpunit": "^10",
         "thecodingmachine/phpstan-strict-rules": "^1.0"
     },
-    "suggest": {
-    },
+    "suggest": {},
     "autoload": {
         "psr-4": {
             "FireflyIII\\": "app/",
diff --git a/composer.lock b/composer.lock
index 6e709a93d4..0c43ded69a 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "58ae8806859163b7e368713d917a12e0",
+    "content-hash": "9cfa71fcc341ecf39399d0a0ff39dd69",
     "packages": [
         {
             "name": "bacon/bacon-qr-code",
@@ -6026,6 +6026,178 @@
             },
             "time": "2023-02-20T14:31:09+00:00"
         },
+        {
+            "name": "symfony/cache",
+            "version": "v7.0.4",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/cache.git",
+                "reference": "fc822951dd360a593224bb2cef90a087d0dff60f"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/cache/zipball/fc822951dd360a593224bb2cef90a087d0dff60f",
+                "reference": "fc822951dd360a593224bb2cef90a087d0dff60f",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=8.2",
+                "psr/cache": "^2.0|^3.0",
+                "psr/log": "^1.1|^2|^3",
+                "symfony/cache-contracts": "^2.5|^3",
+                "symfony/service-contracts": "^2.5|^3",
+                "symfony/var-exporter": "^6.4|^7.0"
+            },
+            "conflict": {
+                "doctrine/dbal": "<3.6",
+                "symfony/dependency-injection": "<6.4",
+                "symfony/http-kernel": "<6.4",
+                "symfony/var-dumper": "<6.4"
+            },
+            "provide": {
+                "psr/cache-implementation": "2.0|3.0",
+                "psr/simple-cache-implementation": "1.0|2.0|3.0",
+                "symfony/cache-implementation": "1.1|2.0|3.0"
+            },
+            "require-dev": {
+                "cache/integration-tests": "dev-master",
+                "doctrine/dbal": "^3.6|^4",
+                "predis/predis": "^1.1|^2.0",
+                "psr/simple-cache": "^1.0|^2.0|^3.0",
+                "symfony/config": "^6.4|^7.0",
+                "symfony/dependency-injection": "^6.4|^7.0",
+                "symfony/filesystem": "^6.4|^7.0",
+                "symfony/http-kernel": "^6.4|^7.0",
+                "symfony/messenger": "^6.4|^7.0",
+                "symfony/var-dumper": "^6.4|^7.0"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Component\\Cache\\": ""
+                },
+                "classmap": [
+                    "Traits/ValueWrapper.php"
+                ],
+                "exclude-from-classmap": [
+                    "/Tests/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Nicolas Grekas",
+                    "email": "p@tchwork.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Provides extended PSR-6, PSR-16 (and tags) implementations",
+            "homepage": "https://symfony.com",
+            "keywords": [
+                "caching",
+                "psr6"
+            ],
+            "support": {
+                "source": "https://github.com/symfony/cache/tree/v7.0.4"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2024-02-22T20:27:20+00:00"
+        },
+        {
+            "name": "symfony/cache-contracts",
+            "version": "v3.4.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/cache-contracts.git",
+                "reference": "1d74b127da04ffa87aa940abe15446fa89653778"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/cache-contracts/zipball/1d74b127da04ffa87aa940abe15446fa89653778",
+                "reference": "1d74b127da04ffa87aa940abe15446fa89653778",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=8.1",
+                "psr/cache": "^3.0"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-main": "3.4-dev"
+                },
+                "thanks": {
+                    "name": "symfony/contracts",
+                    "url": "https://github.com/symfony/contracts"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Contracts\\Cache\\": ""
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Nicolas Grekas",
+                    "email": "p@tchwork.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Generic abstractions related to caching",
+            "homepage": "https://symfony.com",
+            "keywords": [
+                "abstractions",
+                "contracts",
+                "decoupling",
+                "interfaces",
+                "interoperability",
+                "standards"
+            ],
+            "support": {
+                "source": "https://github.com/symfony/cache-contracts/tree/v3.4.0"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2023-09-25T12:52:38+00:00"
+        },
         {
             "name": "symfony/console",
             "version": "v6.4.4",
@@ -6483,6 +6655,70 @@
             ],
             "time": "2023-05-23T14:45:45+00:00"
         },
+        {
+            "name": "symfony/expression-language",
+            "version": "v6.4.3",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/expression-language.git",
+                "reference": "b4a4ae33fbb33a99d23c5698faaecadb76ad0fe4"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/expression-language/zipball/b4a4ae33fbb33a99d23c5698faaecadb76ad0fe4",
+                "reference": "b4a4ae33fbb33a99d23c5698faaecadb76ad0fe4",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=8.1",
+                "symfony/cache": "^5.4|^6.0|^7.0",
+                "symfony/deprecation-contracts": "^2.5|^3",
+                "symfony/service-contracts": "^2.5|^3"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Component\\ExpressionLanguage\\": ""
+                },
+                "exclude-from-classmap": [
+                    "/Tests/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Fabien Potencier",
+                    "email": "fabien@symfony.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Provides an engine that can compile and evaluate expressions",
+            "homepage": "https://symfony.com",
+            "support": {
+                "source": "https://github.com/symfony/expression-language/tree/v6.4.3"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2024-01-23T14:51:35+00:00"
+        },
         {
             "name": "symfony/finder",
             "version": "v6.4.0",
@@ -8584,6 +8820,80 @@
             ],
             "time": "2024-02-15T11:23:52+00:00"
         },
+        {
+            "name": "symfony/var-exporter",
+            "version": "v7.0.4",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/var-exporter.git",
+                "reference": "dfb0acb6803eb714f05d97dd4c5abe6d5fa9fe41"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/var-exporter/zipball/dfb0acb6803eb714f05d97dd4c5abe6d5fa9fe41",
+                "reference": "dfb0acb6803eb714f05d97dd4c5abe6d5fa9fe41",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=8.2"
+            },
+            "require-dev": {
+                "symfony/var-dumper": "^6.4|^7.0"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Component\\VarExporter\\": ""
+                },
+                "exclude-from-classmap": [
+                    "/Tests/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Nicolas Grekas",
+                    "email": "p@tchwork.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Allows exporting any serializable PHP data structure to plain PHP code",
+            "homepage": "https://symfony.com",
+            "keywords": [
+                "clone",
+                "construct",
+                "export",
+                "hydrate",
+                "instantiate",
+                "lazy-loading",
+                "proxy",
+                "serialize"
+            ],
+            "support": {
+                "source": "https://github.com/symfony/var-exporter/tree/v7.0.4"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2024-02-26T10:35:24+00:00"
+        },
         {
             "name": "therobfonz/laravel-mandrill-driver",
             "version": "5.0.0",
diff --git a/resources/lang/en_US/validation.php b/resources/lang/en_US/validation.php
index 5d2abd4939..362a3cc502 100644
--- a/resources/lang/en_US/validation.php
+++ b/resources/lang/en_US/validation.php
@@ -46,6 +46,7 @@ return [
     'reconciled_forbidden_field'      => 'This transaction is already reconciled, you cannot change the ":field"',
     'deleted_user'                    => 'Due to security constraints, you cannot register using this email address.',
     'rule_trigger_value'              => 'This value is invalid for the selected trigger.',
+    'rule_action_expression'          => 'Invalid expression. :error',
     'rule_action_value'               => 'This value is invalid for the selected action.',
     'file_already_attached'           => 'Uploaded file ":name" is already attached to this object.',
     'file_attached'                   => 'Successfully uploaded file ":name".',
diff --git a/routes/api.php b/routes/api.php
index 0bf6c67c65..dfb7da5268 100644
--- a/routes/api.php
+++ b/routes/api.php
@@ -606,6 +606,8 @@ Route::group(
         Route::put('{rule}', ['uses' => 'UpdateController@update', 'as' => 'update']);
         Route::delete('{rule}', ['uses' => 'DestroyController@destroy', 'as' => 'delete']);
 
+        Route::post('validate-expression', ['uses' => 'ExpressionController@validateExpression', 'as' => 'validate']);
+
         Route::get('{rule}/test', ['uses' => 'TriggerController@testRule', 'as' => 'test']);
         // TODO give results back
         Route::post('{rule}/trigger', ['uses' => 'TriggerController@triggerRule', 'as' => 'trigger']);