[GNC] Balance sheet (multicolumn) shows Assets != Liabilities due to rounding of foreign currency amounts

[Tamar Hamlyn]

This is now being tracked as bug 799770:
https://bugs.gnucash.org/show_bug.cgi?id=799770

On Fri, 29 May 2026 at 00:30, Tamar Hamlyn <hamlynt at gmail.com> wrote:
>
> Two additional screenshots (adding foreign currency amounts and
> exchange rates to both reports) might help show this more clearly,
> please refer attached.
>
>
> On Thu, 28 May 2026 at 19:32, Tamar Hamlyn <hamlynt at gmail.com> wrote:
> >
> > Hi GnuCash users,
> >
> > I searched the bug tracker but couldn't find this specific issue
> > documented below.
> >
> > Kind regards,
> > Tamar.
> >
> > Issue: Balance sheet (multicolumn) shows Assets != Liabilities due to
> > rounding of foreign currency amounts
> >
> > Version
> > -------
> > GnuCash 5.15, macOS
> >
> > Issue
> > -----
> > Generating a balance sheet (multicolumn) can produce asset total !=
> > liability total, due to rounding of foreign currency amounts. Standard
> > balance sheet is unaffected.
> >
> > Steps to reproduce
> > ------------------
> > A test gnucash file with transactions below is attached.
> >
> > New book:
> > Choose reporting currency: AUD
> >
> > New accounts under Current Assets:
> > Bank 1(JPY)
> > Bank 2(JPY)
> >
> > Existing Equity account:
> > Opening balances(AUD)
> >
> > Transactions (entering the AUD quantity in the "to amount" field in
> > the exchange rate window):
> > Bank 1: JPY 500k / Opening balances: AUD 3,333.33
> > Bank 2: JPY 200k / Opening balances: AUD 1,333.33
> >
> > Prices:
> > Tools, Price Database, expand Currencies to JPY, add a new
> > end-of-period exchange rate of:
> > 2026-06-30: 0.00666665
> >
> > Note the slight exchange rate difference with the transaction-derived
> > rate of 0.00666666. This difference is what triggers divergent
> > rounding between the two reports.
> >
> > Run report:
> > Balance sheet (multicolumn). Report Options, Commodities tab: set
> > reporting currency to AUD, set price source to last up through report
> > date.
> > For comparison, also run standard balance sheet. Apply same report
> > options in Commodities tab: set reporting currency to AUD, set price
> > source to last up through report date.
> >
> > Actual behaviour
> > ----------------
> > Balance sheet (multicolumn) does not balance: assets != liabilities.
> > Assets total from balance sheet report is: AUD 4,666.65
> > Liabilities total from balance sheet report is: AUD 4,666.66
> >
> > Note the 1 cent difference. Balance sheet (standard) displays correct
> > behaviour, assets and liabilities both total AUD 4,666.66.
> >
> > Desired behaviour
> > -----------------
> > Balance sheet should ALWAYS balance.
> >
> > If balance sheet totals do not match, this suggests an accounting
> > error and invites questions about errors or inaccuracies. It makes the
> > balance sheet report invalid by definition.
> >
> > Possible cause
> > --------------
> > The possible cause might relate to the multicolumn report using a
> > round-then-sum approach, while the standard report uses
> > sum-then-round.
> >
> > The current behaviour in balance sheet (multicolumn) is consistent
> > with the following:
> > - First convert child foreign currency amount to a corresponding
> > (rounded) amount in reporting currency. This involves multiple
> > conversions and applies rounding to every conversion.
> > - Then sum the resulting rounded reporting currency amounts to produce
> > intermediate and top-level reporting currency totals.
> > This approach accumulates rounding errors at each level in the account
> > hierarchy, which in turn results in the top-level discrepancy in
> > totals. It is a round-then-sum approach.
> >
> > Possible fix
> > ------------
> > If strict equality between assets and liability is desirable, then
> > balance sheet (multicolumn) report should instead do the following:
> > - First, determine all intermediate and top-level foreign currency
> > quantities, by aggregating all child foreign currency quantities at
> > each point in the account hierarchy.
> > - Convert each foreign currency total at each level in the account
> > hierarchy to the reporting currency amount as a single conversion.
> > Present these totals in the report.
> > This sum-then-round approach only performs a single rounding operation
> > as the last step at each level of the account hierarchy. This ensures
> > that maximum accuracy is retained for account totals, as they are
> > constructed directly from their local-currency components. Notably
> > this approach does not re-use rounded subtotals to construct parent
> > account amounts.
> >
> > Discussion
> > ----------
> > While the sum-then-round approach can ensure the balance sheet does
> > balance, it also means that report subtotals and totals may not
> > reflect the sum of their displayed sub-accounts and subtotals. Is it
> > desirable to prioritise line-item consistency over balance-sheet
> > equality?
> >
> > I'd be grateful for feedback from users or devs who have encountered
> > this issue, or who are familiar with the development history, who have
> > views either way on which approach might be preferred.
> >
> > Real-world impact
> > -----------------
> > The above rounding errors mean that a real-world balance sheet does
> > not balance in approximately 5 out of the past 10 years. The accounts
> > contain assets across around 6 foreign currencies, with relatively
> > infrequent changes in holdings throughout the history.
> >
> > There are no specific triggers for the mismatched balance sheet
> > totals, other than the randomness of rounding foreign currency
> > subtotals and their conversion at the relevant exchange rates in
> > effect at each balance sheet date.
> >
> > AI usage
> > --------
> > The explanation above was written by myself after testing the above
> > steps manually in GnuCash. I then ran my draft through Claude which
> > made minor changes to grammar and clarity of explanation.
> >
> > Attachments
> > -----------
> > 1 General Journal.png
> > 2 Balance Sheet Multicolumn.png
> > 3 Balance Sheet Standard.png
> > 4 test-balancesheet-multicolumn.gnucash (XML)