diff --git a/gnucash/report/report-utilities.scm b/gnucash/report/report-utilities.scm
index 331be6ce01..267c42474e 100644
--- a/gnucash/report/report-utilities.scm
+++ b/gnucash/report/report-utilities.scm
@@ -303,6 +303,25 @@
 (define (gnc-commodity-collector-allzero? collector)
   (every zero? (map cdr (collector 'format cons #f))))
 
+;; (gnc:collector+ collectors ...) equiv to (+ collectors ...) and
+;; outputs: a collector
+(define (gnc:collector+ . collectors)
+  (let ((res (gnc:make-commodity-collector)))
+    (for-each (lambda (coll) (res 'merge coll #f)) collectors)
+    res))
+
+;; (gnc:collectors- collectors ...) equiv to (- collectors ...), can
+;; also negate single-argument collector. outputs collector
+(define gnc:collector-
+  (case-lambda
+    (() (error "gnc:collector- needs at least 1 collector argument"))
+    ((coll) (gnc:collector- (gnc:make-commodity-collector) coll))
+    ((coll . rest)
+     (let ((res (gnc:make-commodity-collector)))
+       (res 'merge coll #f)
+       (res 'minusmerge (apply gnc:collector+ rest) #f)
+       res))))
+
 ;; add any number of gnc-monetary objects into a commodity-collector
 ;; usage: (gnc:monetaries-add monetary1 monetary2 ...)
 ;; output: a commodity-collector object
@@ -341,7 +360,7 @@
   (define (amount->monetary bal)
     (gnc:make-gnc-monetary (xaccAccountGetCommodity account) bal))
   (let loop ((splits (xaccAccountGetSplitList account))
-             (dates-list (stable-sort! dates-list <))
+             (dates-list (sort dates-list <))
              (currentbal 0)
              (lastbal 0)
              (balancelist '()))
diff --git a/gnucash/report/report.scm b/gnucash/report/report.scm
index f834c46085..75ce728317 100644
--- a/gnucash/report/report.scm
+++ b/gnucash/report/report.scm
@@ -683,6 +683,8 @@
 (export gnc:accounts-and-all-descendants)
 (export gnc:make-value-collector)
 (export gnc:make-commodity-collector)
+(export gnc:collector+)
+(export gnc:collector-)
 (export gnc:commodity-collector-get-negated)
 (export gnc:account-get-balances-at-dates)
 (export gnc:account-get-comm-balance-at-date)
diff --git a/gnucash/report/reports/locale-specific/de_DE/taxtxf.scm b/gnucash/report/reports/locale-specific/de_DE/taxtxf.scm
index c75205e056..aa205f066c 100644
--- a/gnucash/report/reports/locale-specific/de_DE/taxtxf.scm
+++ b/gnucash/report/reports/locale-specific/de_DE/taxtxf.scm
@@ -505,11 +505,7 @@
                                 (validate (reverse 
                                            (gnc-account-get-children-sorted
                                             (gnc-get-current-root-account))))))
-         (book (if selected-accounts
-                   (gnc-account-get-book (if (pair? selected-accounts)
-                                             (car selected-accounts)
-                                             selected-accounts))
-                   #f))
+         (book (gnc-get-current-book))
          (generations (if (pair? selected-accounts)
                           (apply max (map (lambda (x) (num-generations x 1))
                                           selected-accounts))
@@ -772,12 +768,7 @@
 	  (to-year    (gnc-print-time64 to-value "%Y"))
           (today-date (gnc-print-time64 (time64CanonicalDayTime (current-time))
                                         "%d.%m.%Y"))
-	  (tax-nr (unless book
-                      (or
-                       (gnc:option-get-value book gnc:*tax-label* gnc:*tax-nr-label*)
-                       "")
-                      ""))
-	  )
+	  (tax-nr (gnc:option-get-value book gnc:*tax-label* gnc:*tax-nr-label*)))
 
       ;; Now, the main body
       ;; Reset all the balance collectors
diff --git a/gnucash/report/reports/standard/balsheet-pnl.scm b/gnucash/report/reports/standard/balsheet-pnl.scm
index e6ff55eeb8..678430cee8 100644
--- a/gnucash/report/reports/standard/balsheet-pnl.scm
+++ b/gnucash/report/reports/standard/balsheet-pnl.scm
@@ -961,9 +961,8 @@ also show overall period profit & loss."))
                               asset-liability
                               (lambda (acc)
                                 (gnc:account-get-comm-value-at-date acc date #f))))
-                            (unrealized (gnc:make-commodity-collector)))
-                       (unrealized 'merge asset-liability-basis #f)
-                       (unrealized 'minusmerge asset-liability-balance #f)
+                            (unrealized (gnc:collector- asset-liability-basis
+                                                        asset-liability-balance)))
                        (monetaries->exchanged
                         unrealized common-currency price-source date)))))
              (retained-earnings-fn
diff --git a/gnucash/report/reports/standard/budget.scm b/gnucash/report/reports/standard/budget.scm
index e361e914b9..2863dc7f38 100644
--- a/gnucash/report/reports/standard/budget.scm
+++ b/gnucash/report/reports/standard/budget.scm
@@ -317,17 +317,6 @@
                   (gnc-budget-get-account-period-actual-value budget acct period))
                 periodlist)))
 
-    (define (flatten lst)
-      (reverse!
-       (let loop ((lst lst) (result '()))
-         (if (null? lst)
-             result
-             (let ((elt (car lst))
-                   (rest (cdr lst)))
-               (if (pair? elt)
-                   (loop rest (append (loop elt '()) result))
-                   (loop rest (cons elt result))))))))
-
     ;; Adds a line to the budget report.
     ;;
     ;; Parameters:
@@ -342,7 +331,7 @@
              column-list exchange-fn)
       (let* ((comm (xaccAccountGetCommodity acct))
              (reverse-balance? (gnc-reverse-balance acct))
-             (allperiods (filter number? (flatten column-list)))
+             (allperiods (filter number? (gnc:list-flatten column-list)))
              (total-periods (if accumulate?
                                 (iota (1+ (apply max allperiods)))
                                 allperiods))
@@ -396,6 +385,7 @@
                                budget acct total-periods))
                    (act-total (gnc:get-account-periodlist-actual-value
                                budget acct total-periods))
+                   (act-total (if reverse-balance? (- act-total) act-total))
                    (dif-total (if income-acct?
                                   (- act-total bgt-total)
                                   (- bgt-total act-total))))
diff --git a/gnucash/report/reports/standard/category-barchart.scm b/gnucash/report/reports/standard/category-barchart.scm
index 27a86beae6..952d2cd866 100644
--- a/gnucash/report/reports/standard/category-barchart.scm
+++ b/gnucash/report/reports/standard/category-barchart.scm
@@ -336,12 +336,6 @@ developing over time"))
                   c report-currency
                   (lambda (a b) (exchange-fn a b date)))))))
 
-          (define (collector-minus a b)
-            (let ((coll (gnc:make-commodity-collector)))
-              (coll 'merge a #f)
-              (coll 'minusmerge b #f)
-              coll))
-
           ;; copy of gnc:not-all-zeros using gnc-monetary
           (define (not-all-zeros data)
             (cond ((gnc:gnc-monetary? data) (not (zero? (gnc:gnc-monetary-amount data))))
@@ -396,8 +390,8 @@ developing over time"))
                           (cdr dates-list)
                           (cons (if do-intervals?
                                     (collector->monetary
-                                     (collector-minus (cadr list-of-mon-collectors)
-                                                      (car list-of-mon-collectors))
+                                     (gnc:collector- (cadr list-of-mon-collectors)
+                                                     (car list-of-mon-collectors))
                                      (cadr dates-list))
                                     (collector->monetary
                                      (car list-of-mon-collectors)
diff --git a/gnucash/report/reports/standard/customer-summary.scm b/gnucash/report/reports/standard/customer-summary.scm
index bde2d86946..98312c7c6f 100644
--- a/gnucash/report/reports/standard/customer-summary.scm
+++ b/gnucash/report/reports/standard/customer-summary.scm
@@ -261,11 +261,6 @@
                  (member (xaccSplitGetAccount s) accounts))
                splits))))
 
-(define (coll-minus minuend subtrahend)
-  (let ((coll (gnc:make-commodity-collector)))
-    (coll 'merge minuend #f)
-    (coll 'minusmerge subtrahend #f)
-    coll))
 
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
@@ -347,7 +342,7 @@
                                (sales (gnc:commodity-collector-get-negated
                                        (filter-splits splits sales-accounts)))
                                (expense (filter-splits splits expense-accounts))
-                               (profit (coll-minus sales expense)))
+                               (profit (gnc:collector- sales expense)))
                           (list owner profit sales expense)))
                       ownerlist))
             (sortingtable '()))
@@ -402,9 +397,10 @@
 
         ;; Add the "No Customer" lines to the sortingtable for sorting
         ;; as well
-        (let* ((other-sales (coll-minus toplevel-total-sales total-sales))
-               (other-expense (coll-minus toplevel-total-expense total-expense))
-               (other-profit (coll-minus other-sales  other-expense)))
+        (let* ((other-sales (gnc:collector- toplevel-total-sales total-sales))
+               (other-expense (gnc:collector- toplevel-total-expense
+                                                  total-expense))
+               (other-profit (gnc:collector- other-sales other-expense)))
           (for-each
            (lambda (comm)
              (let* ((profit (cadr (other-profit 'getpair comm #f)))
@@ -478,7 +474,8 @@
                  (gnc:make-html-text (gnc:html-markup/attr/no-end "hr" "noshade")))))
 
         ;; Summary lines - 1 per currency
-        (let ((total-profit (coll-minus toplevel-total-sales toplevel-total-expense)))
+        (let ((total-profit (gnc:collector- toplevel-total-sales
+                                            toplevel-total-expense)))
           (for-each
            (lambda (comm)
              (let* ((profit (cadr (total-profit 'getpair comm #f)))
diff --git a/gnucash/report/reports/standard/invoice.scm b/gnucash/report/reports/standard/invoice.scm
index aec6eca231..88e5482c71 100644
--- a/gnucash/report/reports/standard/invoice.scm
+++ b/gnucash/report/reports/standard/invoice.scm
@@ -727,6 +727,7 @@ for styling the invoice. Please see the exported report for the CSS class names.
          (fax (gnc:company-info book gnc:*company-fax*))
          (email (gnc:company-info book gnc:*company-email*))
          (url (gnc:company-info book gnc:*company-url*))
+         (taxnr (gnc:option-get-value book gnc:*tax-label* gnc:*tax-nr-label*))
          (taxid (gnc:company-info book gnc:*company-id*)))
 
     (if (and name (not (string-null? name)))
@@ -764,6 +765,11 @@ for styling the invoice. Please see the exported report for the CSS class names.
                                            (gnc:make-html-div/markup
                                             "maybe-align-right company-tax-id" taxid))))
 
+    (if (and taxnr (not (string-null? taxnr)))
+        (gnc:html-table-append-row!
+         table (list (gnc:make-html-div/markup
+                      "maybe-align-right company-tax-nr" taxnr))))
+
     table))
 
 (define (reg-renderer report-obj)
diff --git a/gnucash/report/reports/standard/net-charts.scm b/gnucash/report/reports/standard/net-charts.scm
index 5a694ca9f7..bca40aa83d 100644
--- a/gnucash/report/reports/standard/net-charts.scm
+++ b/gnucash/report/reports/standard/net-charts.scm
@@ -254,12 +254,6 @@
     ;; conversion function above. Returns a list of gnc-monetary.
     (define (process-datelist account-balances dates left-col?)
 
-      (define (collector-minus coll1 coll2)
-        (let ((res (gnc:make-commodity-collector)))
-          (res 'merge coll1 #f)
-          (res 'minusmerge coll2 #f)
-          res))
-
       (define accountlist
         (if inc-exp?
             (if left-col?
@@ -297,7 +291,7 @@
                   (cons
                    (collector->monetary
                     (if inc-exp?
-                        (collector-minus (car acct-balances) (cadr acct-balances))
+                        (gnc:collector- (car acct-balances) (cadr acct-balances))
                         (car acct-balances))
                     (if inc-exp? (cadr dates) (car dates)))
                    result)))))
diff --git a/gnucash/report/reports/standard/owner-report.scm b/gnucash/report/reports/standard/owner-report.scm
index 803fffde90..4a5b62903e 100644
--- a/gnucash/report/reports/standard/owner-report.scm
+++ b/gnucash/report/reports/standard/owner-report.scm
@@ -746,8 +746,8 @@
      (end-date (gnc:time64-end-day-time 
                (gnc:date-option-absolute-time
                (opt-val gnc:pagename-general optname-to-date))))
-     (book (gnc-account-get-book account))
-     (date-format (if (not (null? book)) (gnc:options-fancy-date book)))
+     (book (gnc-get-current-book))
+     (date-format (gnc:options-fancy-date book))
      (type (opt-val "__reg" "owner-type"))
      (owner-descr (owner-string type))
      (date-type (opt-val gnc:pagename-general optname-date-driver))
diff --git a/gnucash/report/reports/standard/test/test-trial-balance.scm b/gnucash/report/reports/standard/test/test-trial-balance.scm
index d0f4dfe7e8..3d34c45a35 100644
--- a/gnucash/report/reports/standard/test/test-trial-balance.scm
+++ b/gnucash/report/reports/standard/test/test-trial-balance.scm
@@ -62,13 +62,15 @@
 (define (test-trial-balance)
   (let* ((options (gnc:make-report-options uuid))
          (account-alist (create-test-data))
+         (gbp-bank (assoc-ref account-alist "GBP Bank"))
+         (usd-bank (assoc-ref account-alist "Bank"))
          (expense (assoc-ref account-alist "Expenses"))
          (equity (assoc-ref account-alist "Equity"))
          (income (assoc-ref account-alist "Income"))
          (bank (assoc-ref account-alist "Bank")))
 
     (gnc-commodity-set-user-symbol
-     (xaccAccountGetCommodity (assoc-ref account-alist "GBP Bank"))
+     (xaccAccountGetCommodity gbp-bank)
      "#")
 
     (let ((closing-txn (env-transfer #f 30 06 2003 expense equity
@@ -167,6 +169,18 @@
         (sxml->table-row-col sxml 1 #f 10))
 
       (test-equal "work-sheet bs credits"
-        ' ("$3.00" "$2,356.00" "$2,359.00" "$760.00" "$3,119.00")
+        '("$3.00" "$2,356.00" "$2,359.00" "$760.00" "$3,119.00")
         (sxml->table-row-col sxml 1 #f 11)))
-    ))
+
+    ;; A couple of transactions which involve foreign currency
+    ;; conversions. We'll set the currencies to GBP and USD.
+    (env-transfer-foreign #f 15 01 2000 gbp-bank usd-bank
+                          10 14 #:description "GBP 10 to USD 14")
+    (env-transfer-foreign #f 15 02 2000 usd-bank gbp-bank
+                          9  8 #:description "USD 9 to GBP 8")
+
+    (set-option options "General" "Report variation" 'current)
+    (let ((sxml (options->sxml options "test-unrealized-gain")))
+      (test-equal "unrealized losses"
+        '("Unrealized Gains" "$3.25")
+        (sxml->table-row-col sxml 1 -2 #f)))))
diff --git a/gnucash/report/reports/standard/trial-balance.scm b/gnucash/report/reports/standard/trial-balance.scm
index bd0f13a442..80ecfdc9a8 100644
--- a/gnucash/report/reports/standard/trial-balance.scm
+++ b/gnucash/report/reports/standard/trial-balance.scm
@@ -152,9 +152,7 @@
          (amt (and sum (gnc:gnc-monetary-amount sum)))
          (neg? (and amt (negative? amt)))
          (bal (if neg?
-                  (let ((bal (gnc:make-commodity-collector)))
-                    (bal 'minusmerge signed-balance #f)
-                    bal)
+                  (gnc:commodity-collector-get-negated signed-balance)
                   signed-balance))
          (bal-sum (gnc:sum-collector-commodity
                    bal
@@ -512,36 +510,21 @@
           ;;
           ;; This procedure returns a commodity collector.
           (define (collect-unrealized-gains)
+            (define (acct->bal acct)
+              (gnc:account-get-comm-balance-at-date acct end-date #f))
             (if (eq? price-source 'average-cost)
                 ;; No need to calculate if doing valuation at cost.
                 (gnc:make-commodity-collector)
-                (let ((book-balance (gnc:make-commodity-collector))
-                      (unrealized-gain-collector (gnc:make-commodity-collector))
-                      (cost-fn (gnc:case-exchange-fn
-                                'average-cost report-commodity end-date)))
-
-                  ;; Calculate book balance.
-                  ;; assets - liabilities - equity; normally 0
-                  (for-each
-                   (lambda (acct)
-                     (book-balance
-                      'merge
-                      (gnc:account-get-comm-balance-at-date acct end-date #f)
-                      #f))
-                   all-accounts)
-
-                  (let ((value (gnc:gnc-monetary-amount
-                                (gnc:sum-collector-commodity
-                                 book-balance report-commodity exchange-fn)))
-                        (cost (gnc:gnc-monetary-amount
-                               (gnc:sum-collector-commodity
-                                book-balance report-commodity cost-fn))))
-
-                    ;; Get the unrealized gain or loss (value minus cost).
-                    (unrealized-gain-collector
-                     'add report-commodity (- value cost))
-                    unrealized-gain-collector))))
-
+                (let* ((cost-fn (gnc:case-exchange-fn
+                                 'average-cost report-commodity end-date))
+                       (acct-balances (map acct->bal all-accounts))
+                       (book-balance (apply gnc:collector+ acct-balances))
+                       (value (gnc:sum-collector-commodity
+                               book-balance report-commodity exchange-fn))
+                       (cost (gnc:sum-collector-commodity
+                              book-balance report-commodity cost-fn)))
+                  ;; Get the unrealized gain or loss (value minus cost).
+                  (gnc:monetaries-add value (gnc:monetary-neg cost)))))
 
           ;; set default cell alignment
           (gnc:html-table-set-style!
@@ -667,12 +650,6 @@
                  splits)
                 total))
 
-            (define (coll-minus . collectors)
-              (let ((res (gnc:make-commodity-collector)))
-                (res 'merge (car collectors) #f)
-                (for-each (lambda (mon) (res 'minusmerge mon #f)) (cdr collectors))
-                res))
-
             (while (< row rows)
               (let* ((env (gnc:html-acct-table-get-row-env acct-table row))
                      (acct (get-val env 'account))
@@ -684,21 +661,19 @@
                      (pos-adjusting
                       (and ga-or-is? (sum-account-splits acct adjusting-splits #t)))
                      (neg-adjusting
-                      (and ga-or-is? (coll-minus adjusting pos-adjusting)))
-                     (pre-closing-bal (coll-minus curr-bal closing))
-                     (pre-adjusting-bal (coll-minus pre-closing-bal adjusting))
-                     (atb (if is?
-                              (let* ((debit (gnc:make-commodity-collector))
-                                     (credit (gnc:make-commodity-collector)))
-                                (debit 'merge pos-adjusting #f)
-                                (credit 'merge neg-adjusting #f)
-                                (if (double-col
-                                     'credit-q pre-adjusting-bal
-                                     report-commodity exchange-fn show-fcur?)
-                                    (credit 'merge pre-adjusting-bal #f)
-                                    (debit 'merge pre-adjusting-bal #f))
-                                (list debit credit))
-                              pre-closing-bal)))
+                      (and ga-or-is? (gnc:collector- adjusting pos-adjusting)))
+                     (pre-closing-bal (gnc:collector- curr-bal closing))
+                     (pre-adjusting-bal (gnc:collector- pre-closing-bal
+                                                        adjusting))
+                     (atb (cond ((not is?) pre-closing-bal)
+                                ((double-col 'credit-q pre-adjusting-bal
+                                             report-commodity exchange-fn show-fcur?)
+                                 (list (gnc:collector+ pos-adjusting)
+                                       (gnc:collector+ neg-adjusting
+                                                       pre-adjusting-bal)))
+                                (else
+                                 (list (gnc:collector+ pos-adjusting pre-adjusting-bal)
+                                       (gnc:collector+ neg-adjusting))))))
 
                 ;; curr-bal = account-bal with closing & adj entries
                 ;; pre-closing-bal = account-bal with adj entries only
@@ -865,8 +840,8 @@
                  (tot-abs-amt-cell bs-credits))
                 '())))
           (if (eq? report-variant 'work-sheet)
-              (let* ((net-is (gnc:make-commodity-collector))
-                     (net-bs (gnc:make-commodity-collector))
+              (let* ((net-is (gnc:collector- is-debits is-credits))
+                     (net-bs (gnc:collector- bs-debits bs-credits))
                      (tot-is (gnc:make-commodity-collector))
                      (tot-bs (gnc:make-commodity-collector))
                      (is-entry #f)
@@ -875,10 +850,6 @@
                      (bs-credit? #f)
                      (tbl-width (+ account-cols (* 2 bs-col) 2))
                      (this-row (gnc:html-table-num-rows build-table)))
-                (net-is 'merge is-debits #f)
-                (net-is 'minusmerge is-credits #f)
-                (net-bs 'merge bs-debits #f)
-                (net-bs 'minusmerge bs-credits #f)
                 (set! is-entry
                   (double-col 'entry net-is report-commodity exchange-fn show-fcur?))
                 (set! is-credit?
diff --git a/gnucash/report/test/test-report-utilities.scm b/gnucash/report/test/test-report-utilities.scm
index 9a5d71be7f..6fe13ced2e 100644
--- a/gnucash/report/test/test-report-utilities.scm
+++ b/gnucash/report/test/test-report-utilities.scm
@@ -212,6 +212,21 @@
         (gnc:make-gnc-monetary USD 25)
         (coll-A 'getmonetary USD #f))
 
+      (test-equal "gnc:collector+"
+        '(("USD" . 50) ("GBP" . -20))
+        (collector->list
+         (gnc:collector+ coll-A coll-A coll-B)))
+
+      (test-equal "gnc:collector- 1 arg"
+        '(("GBP" . 20) ("USD" . -25))
+        (collector->list
+         (gnc:collector- coll-A)))
+
+      (test-equal "gnc:collector- 3 args"
+        '(("USD" . 25) ("GBP" . -60))
+        (collector->list
+         (gnc:collector- coll-A coll-B coll-B)))
+
       (test-equal "gnc:commodity-collector-get-negated"
         '(("USD" . -25) ("GBP" . 20))
         (collector->list
diff --git a/libgnucash/app-utils/app-utils.scm b/libgnucash/app-utils/app-utils.scm
index 0b73c0378a..36ce6e8fd5 100644
--- a/libgnucash/app-utils/app-utils.scm
+++ b/libgnucash/app-utils/app-utils.scm
@@ -276,6 +276,8 @@
 (define gnc:*company-contact* (N_ "Company Contact Person"))
 (define gnc:*fancy-date-label* (N_ "Fancy Date Format"))
 (define gnc:*fancy-date-format* (N_ "custom"))
+(define gnc:*tax-label* (N_ "Tax"))
+(define gnc:*tax-nr-label* (N_ "Tax Number"))
 
 (define (gnc:company-info book key)
   ;; Access company info from key-value pairs for current book
@@ -304,6 +306,7 @@
         gnc:*option-name-currency-accounting* gnc:*option-name-book-currency*
         gnc:*option-name-default-gains-policy*
         gnc:*option-name-default-gain-loss-account*
+        gnc:*tax-label* gnc:*tax-nr-label*
         gnc:*option-name-auto-readonly-days* gnc:*option-name-num-field-source*)
 
 (define gnc:*option-section-budgeting* OPTION-SECTION-BUDGETING)
diff --git a/libgnucash/app-utils/business-prefs.scm b/libgnucash/app-utils/business-prefs.scm
index 9f4a666cad..1e3b7c6d3d 100644
--- a/libgnucash/app-utils/business-prefs.scm
+++ b/libgnucash/app-utils/business-prefs.scm
@@ -157,6 +157,12 @@
     gnc:*option-section-budgeting* gnc:*option-name-default-budget*
     "a" (N_ "Budget to be used when none has been otherwise specified.")))
 
+  ;; Tax Tab
+  (reg-option
+   (gnc:make-string-option
+    gnc:*tax-label* gnc:*tax-nr-label*
+    "a" (N_ "The electronic tax number of your business") ""))
+
   ;; Counters Tab
   (for-each
    (lambda (vals)
diff --git a/libgnucash/scm/test/test-libgnucash-scm-utilities.scm b/libgnucash/scm/test/test-libgnucash-scm-utilities.scm
index efa9c8795d..afe548a101 100644
--- a/libgnucash/scm/test/test-libgnucash-scm-utilities.scm
+++ b/libgnucash/scm/test/test-libgnucash-scm-utilities.scm
@@ -10,6 +10,7 @@
   (test-traverse-vec)
   (test-substring-replace)
   (test-sort-and-delete-duplicates)
+  (test-gnc:list-flatten)
   (test-begin "test-libgnucash-scm-utilities.scm"))
 
 (define (test-traverse-vec)
@@ -87,3 +88,14 @@
     '(1 2 3)
     (sort-and-delete-duplicates '(3 1 2) <))
   (test-end "sort-and-delete-duplicates"))
+
+(define (test-gnc:list-flatten)
+  (test-equal "gnc:list-flatten null"
+    '()
+    (gnc:list-flatten '()))
+  (test-equal "gnc:list-flatten noop"
+    '(1 2 3)
+    (gnc:list-flatten '(1 2 3)))
+  (test-equal "gnc:list-flatten deep"
+    '(1 2 3 4 5 6)
+    (gnc:list-flatten '(1 (2) (() () (((((3))) ())) 4 () ((5) (6)))))))
diff --git a/libgnucash/scm/utilities.scm b/libgnucash/scm/utilities.scm
index aa69e277fa..6665f1b97d 100644
--- a/libgnucash/scm/utilities.scm
+++ b/libgnucash/scm/utilities.scm
@@ -47,6 +47,7 @@
 (export gnc:debug)
 (export addto!)
 (export sort-and-delete-duplicates)
+(export gnc:list-flatten)
 
 ;; Do this stuff very early -- but other than that, don't add any
 ;; executable code until the end of the file if you can help it.
@@ -191,6 +192,17 @@
   (define (kons a b) (if (and (pair? b) (= a (car b))) b (cons a b)))
   (reverse (fold kons '() (sort lst <))))
 
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; flattens an arbitrary deep nested list into simple list.  this is
+;; probably the most efficient algorithm available. '(1 2 (3 4)) -->
+;; '(1 2 3 4)
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+(define (gnc:list-flatten . lst)
+  (reverse
+   (let lp ((e lst) (accum '()))
+     (if (list? e)
+         (fold lp accum e)
+         (cons e accum)))))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; compatibility hack for fixing guile-2.0 string handling. this code
diff --git a/libgnucash/tax/de_DE/tax.scm b/libgnucash/tax/de_DE/tax.scm
index 1fff197efa..34d20dac07 100644
--- a/libgnucash/tax/de_DE/tax.scm
+++ b/libgnucash/tax/de_DE/tax.scm
@@ -49,10 +49,5 @@
 (export txf-asset-categories)
 (export txf-liab-eq-categories)
 
-(define gnc:*tax-label* (N_ "Tax"))
-(define gnc:*tax-nr-label* (N_ "Tax Number"))
-
-(export gnc:*tax-label* gnc:*tax-nr-label*)
-
 (load-from-path "gnucash/locale/de_DE/tax/txf")
 (load-from-path "gnucash/locale/de_DE/tax/txf-help")
diff --git a/libgnucash/tax/de_DE/txf.scm b/libgnucash/tax/de_DE/txf.scm
index c93cdc3f68..92b3d89b75 100644
--- a/libgnucash/tax/de_DE/txf.scm
+++ b/libgnucash/tax/de_DE/txf.scm
@@ -312,16 +312,3 @@ Fehlermeldungen + Dankschreiben an: stoll@bomhardt.de"))
    )
   )
 ))
-
-;;; Register global options in this book
-(define (book-options-generator options)
-  (define (reg-option new-option)
-    (gnc:register-option options new-option))
-
-  (reg-option
-   (gnc:make-string-option
-    gnc:*tax-label* gnc:*tax-nr-label*
-    "a" (N_ "The electronic tax number of your business") ""))
-  )
-
-(gnc-register-kvp-option-generator QOF-ID-BOOK-SCM book-options-generator)