With multicurrency on, a bank can live in its own currency — a USD account in a CAD company. The law that governs it is short: the general ledger never leaves your home currency, and the bank's own-currency position rides on every entry. Each posting that touches a bank account also records the bank-currency amount, so the bank's balance is always known in both denominations — and Cash Position and the bank pickers show the bank's own currency first, with the home-currency equivalent beside it.
Three consequences follow in daily work:
- The amount that moves at the bank is what is recorded. Pay a USD invoice from an account in another currency and the form asks for the amount actually taken from the bank, in the bank's currency, suggesting the converted figure. The bank leg is valued at the stored rate for the document's date; any difference against the document's own frozen rate is a real exchange difference and lands in realized FX (7.11) — spreads are shown, not buried.
- A missing rate blocks; it never guesses. If no stored rate exists for the pair on or before the date, the posting stops and names the pair and the date. Add the rate and post again. There is no path on which the application invents a rate.
- The overdraft guard judges in the bank's own currency. A USD account is sufficient, or short, in dollars — whatever the home-currency translation happens to say that day.
Openings and adoption. A new foreign bank's opening balance is entered in the bank's own currency and converted at the rate you give (7.7) — and from birth its currency balance is carried. A bank that was marked foreign before this design arrived needs one deliberate step: Edit Bank → Adopt currency balance, where the administrator states the bank's true own-currency balance as at adoption, at a stated rate which must exist in the stored rates. Until a bank is adopted, its own-currency balance is simply not shown — the application displays "—" rather than a figure it cannot stand behind — while its home-currency books carry on untouched, because adoption moves no money: it is a memorandum that lets the two denominations agree from that day forward.
A manual journal that touches a foreign bank must state the bank-currency amount line by line — the form asks for it (7.7) — for the same reason: the amount is not decoration; it is the bank's balance.