Multi-currency bookkeeping for US companies
The moment a US business invoices a foreign customer, pays an overseas supplier, or holds a foreign bank account, its books have to deal with more than one currency — and exchange rates that move between the sale and the settlement. Handled loosely, this produces accounts that quietly drift out of accuracy. This guide explains functional currency, how foreign transactions are recorded, and where exchange-rate gains and losses come from.
Start with the functional currency
The first decision is the functional currency — the main currency the business operates and keeps its books in, which for a US company is normally the US dollar. Everything in the accounts is ultimately expressed in this currency; foreign-currency amounts are converted into it to be recorded. Fixing the functional currency matters because it is the anchor: every transaction in euros, pounds, or rupees is translated back to dollars for the books and, in turn, for the tax return. A business that never explicitly sets this ends up converting inconsistently, which is where multi-currency errors begin.
Recording a foreign transaction
A transaction in a foreign currency is recorded at its dollar value on the transaction date, using that day's exchange rate. So an invoice issued in euros is booked at the dollar equivalent on the invoice date. The complication arises on settlement: if the invoice is paid weeks later, the exchange rate has usually moved, so the dollars actually received differ from the dollars originally recorded. That difference is not a change to the sale — it is a separate foreign-exchange gain or loss, recorded in its own account. The underlying revenue stays as first booked; the currency movement is recognised distinctly.
We run multi-currency books for US companies with overseas operations, handling conversions, FX gains and losses, and period-end revaluation.
Avail our bookkeeping servicesBalances that linger, and where this connects
Foreign-currency balances that are still open at period end — an unpaid foreign invoice, a foreign bank account — raise a further step: they may need revaluing at the period-end rate so the accounts reflect their current dollar value, with the movement recorded as an unrealised gain or loss. This is a standard part of the period-end close for a business with foreign activity. Multi-currency issues show up wherever money crosses borders: in payment processors that settle in different currencies, and in receivables owed by foreign customers. Because the tax rules on foreign-currency gains, losses, and which exchange rates to use can be specific, a business with significant foreign dealings should confirm the treatment rather than relying on a single rounded rate.
One invoice, two rates, one gain
The rule that governs this is section 988 of the Internal Revenue Code, which treats gain or loss attributable to a change in exchange rates on a foreign currency denominated payable or receivable as ordinary gain or loss, recognised separately from the underlying transaction. That is the whole reason the two-rate treatment below exists: the sale is measured once, at the spot rate on the transaction date, and everything that happens to the exchange rate afterwards is a separate ordinary item rather than an adjustment to revenue.
Foreign-currency gains and losses are not a market opinion. They are the arithmetic consequence of recording a transaction on one date and settling it on another, and they appear whether or not anyone tracks them.
| Date | Event | Rate | Recorded |
|---|---|---|---|
| 1 March | Invoice raised, €10,000 | 1.08 | Receivable $10,800 |
| 15 April | Payment received, €10,000 | 1.12 | Bank $11,200 |
| 15 April | Difference | — | FX gain $400 |
The entry on settlement is: debit bank $11,200, credit receivable $10,800, credit foreign exchange gain $400. Revenue stays at the $10,800 recorded when the sale happened — the $400 is not extra sales, and pushing it into revenue overstates trading performance and distorts gross margin. Had the rate moved to 1.04 instead, the same mechanics produce a $400 loss.
Revaluing what is still open at period end
Balances still outstanding at a reporting date need restating at the closing rate, and the resulting movement is unrealised until settlement.
| Item | Foreign amount | At booking | At 30 June (1.10) | Movement |
|---|---|---|---|---|
| Receivable from EU customer | €25,000 | $27,000 (1.08) | $27,500 | +$500 |
| Payable to EU supplier | €8,000 | $8,800 (1.10) | $8,800 | Nil |
| EUR bank account | €5,000 | $5,400 (1.08) | $5,500 | +$100 |
Note the direction: a receivable and a payable in the same currency move opposite ways on the same rate change, which is why netting them into a single "FX" figure loses the information. Keep realised and unrealised differences in separate accounts — the first is settled fact, the second reverses next period, and a lender reading a single blended line cannot tell which is which.
Because the rules on which exchange rates are acceptable and how foreign-currency gains and losses are treated for tax are set by the IRS and can be specific to your circumstances, confirm the treatment before relying on a single rounded rate across the year. Related: receivables owed by foreign customers.
Sources
This guide is written against the official and clearly labelled professional references below. Rates, thresholds and portal procedures change between reviews, so open the primary source before relying on a figure.
Questions people also ask
What is a functional currency?
It is the main currency a business operates in and keeps its books in — for a US company, normally the US dollar. Transactions in other currencies are converted into the functional currency to be recorded. Fixing the functional currency first is essential, because every foreign-currency amount is ultimately translated back into it for the accounts and the tax return.
How are foreign-currency transactions recorded?
A transaction in a foreign currency is converted to the functional currency at the exchange rate on the transaction date, and recorded at that dollar amount. If the item is later settled at a different rate — for instance an invoice paid weeks after it was issued — the difference between the two rates is recorded as a foreign-exchange gain or loss.
What is an exchange-rate gain or loss?
It is the profit or loss that arises purely because exchange rates moved between two points in time — such as between invoicing a foreign customer and being paid. If the dollar value received differs from the dollar value originally recorded, the difference is an FX gain or loss. It is a real result of currency movement, recorded separately from the underlying sale or purchase.
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