Key takeaways
What this article covers, in order:
- The $200 that went missing
- Why FX differences happen
- Realized vs unrealized
- Don't mix FX with fees
- Foreign-currency bank accounts
- Month-end FX checklist
When you invoice or get billed in a foreign currency, the exchange rate on the day of the invoice is almost never the rate on the day the money moves. The difference between the two is a foreign exchange (FX) gain or loss. Once you're paid or you pay, it's realized; while the invoice or bill is still open at month-end, it's unrealized.
This post explains both with a worked example, shows how to keep bank fees separate from FX, and gives you a month-end routine so your foreign-currency balances reconcile without guesswork.
The $200 that went missing
Aisha runs a three-person UX design studio in Raleigh. On Sep 1, 2026 she invoiced a client in Berlin €10,000 for a website redesign. Her books are in US dollars, and that day €1 was worth $1.10 (the rates in this post are illustrative). So the invoice went into her books as $11,000 of revenue and $11,000 of accounts receivable.
The client paid in full on Oct 1, 2026. By then the euro had slipped to $1.08. Her bank converted the €10,000 and deposited $10,800.
The invoice said "paid in full." Her AR said $11,000. Her bank said $10,800. Where did $200 go?
Nowhere. It's a realized foreign exchange loss. Nobody short-paid; the currency moved.
Why FX differences happen
Your books have one home currency: US dollars. Every foreign-currency transaction has to be converted into dollars to be recorded. The question is which rate to use, and the answer is: the rate on the day of each transaction.
- The invoice is recorded at the rate on the invoice date
- The payment is recorded at the rate (really, the amount of dollars) on the payment date
If those two rates differ, the dollar amounts differ, and the gap is a gain or a loss.
| Invoice date | Payment date | |
|---|---|---|
| Date | Sep 1, 2026 | Oct 1, 2026 |
| Amount in euros | €10,000 | €10,000 |
| Rate (USD per EUR) | 1.10 | 1.08 |
| Amount in dollars | $11,000 | $10,800 |
| Difference | −$200 (loss) |
If the euro had strengthened to $1.12 instead, she'd have received $11,200 and booked a $200 gain.
For bills it runs the other way. If you owe a supplier in a foreign currency and that currency weakens before you pay, you pay fewer dollars than you recorded, which is a gain. If it strengthens, it's a loss.
Realized vs unrealized
Realized gains and losses
Realized means the transaction is finished. Money moved, the invoice or bill is closed, and the dollar difference is locked in. Aisha's $200 is realized on Oct 1, 2026.
The entry when the payment arrives:
| Account | Debit | Credit |
|---|---|---|
| Checking (USD) | $10,800 | |
| Realized FX loss | $200 | |
| Accounts receivable | $11,000 |
The invoice closes at its full recorded value. The loss shows on the P&L, usually below operating income as an "other expense" line.
Unrealized gains and losses
Unrealized means the invoice or bill is still open at a reporting date, and you're showing what it's worth at today's rate.
Say Aisha closes her books for September 2026 on Sep 30, 2026 and the rate that day is 1.09. The open €10,000 invoice is now worth $10,900, not $11,000. Revaluing it at month-end records a $100 unrealized loss:
| Account | Debit | Credit |
|---|---|---|
| Unrealized FX loss | $100 | |
| Accounts receivable | $100 |
Then, when payment arrives on Oct 1, 2026 at 1.08, the remaining realized loss is measured from the revalued $10,900, so another $100. Total over the two months: still $200.
Different software and different bookkeepers handle revaluation in different ways. Some reverse the unrealized entry at the start of the next month and book the full realized difference on payment. Either way, the total loss over the life of the invoice is the same. Pick one approach and stay consistent. If your foreign-currency balances are large, ask your CPA which method fits your reporting.
Don't mix FX with fees
This is where reconciliations get muddy. When money crosses borders, there are usually three things going on:
- The market exchange rate move (the FX gain or loss)
- The bank's conversion spread (the difference between the market rate and the rate your bank actually gave you)
- Fixed fees (incoming wire fees, intermediary bank fees)
Say Aisha's bank actually deposited $10,765 instead of $10,800, because it deducted a $35 incoming wire fee before crediting her account. She'd record:
| Item | Amount | Where it goes |
|---|---|---|
| Invoice value at booking | $11,000 | Accounts receivable cleared |
| Realized FX loss | $200 | Realized FX loss |
| Incoming wire fee | $35 | Bank fees |
| Cash received | $10,765 | Checking |
Check: $11,000 − $200 − $35 = $10,765.
Keeping fees separate tells you something useful. FX moves are mostly out of your control. Fees aren't. If your FX loss line keeps growing because of fees and spreads, it might be time to look at a different way to receive foreign payments.
The bank's spread is harder to separate because it's baked into the rate. Most small businesses simply let it fall into the realized FX line. That's fine. Just know it's in there.
Foreign-currency bank accounts
Some businesses hold a euro, Canadian dollar or pound account alongside their USD account. In that case:
- Reconcile the foreign account in its own currency first. The euro balance on your statement should match the euro balance in your books exactly.
- The dollar value of that account changes as rates move. That's an unrealized gain or loss on the cash itself, revalued at month-end.
- Transfers between your EUR and USD accounts create realized FX differences at the moment of conversion.
Reconciling in the original currency is the key. If the euros tie out, any dollar difference is FX, not a missing transaction.
Month-end FX checklist
- [ ] Reconcile every foreign-currency bank account in its own currency
- [ ] Match every foreign-currency payment to its invoice or bill
- [ ] Record bank fees separately from FX differences
- [ ] Post realized gains and losses for invoices and bills closed this month
- [ ] Revalue open foreign-currency AR, AP and bank balances at the month-end rate, if your method calls for it
- [ ] Check the total FX gain or loss for the month and make sure it's plausible given how rates moved
- [ ] Note the rate source and date you used
Ways to reduce FX surprises
- Invoice in USD where clients will accept it. The exchange risk moves to them.
- Shorten payment terms for foreign clients. Less time open, less time for rates to move.
- Hold a foreign-currency account if you both receive and spend in that currency, so you convert less often.
- Compare conversion costs. Bank spreads and wire fees vary widely between providers.
How HelloBooks helps
Multi-currency with auto FX is included on the Pro plan ($39.99/month). You can raise invoices and enter bills in a foreign currency, and HelloBooks fills in the exchange rate automatically rather than asking you to look it up. When the payment arrives through your bank feed, it lands in a review list and you record it against the foreign-currency invoice or bill. Pro also includes unlimited bank connections, so you can connect a USD account and a foreign-currency account side by side (you can connect most US banks and credit cards, or import a CSV statement where a feed isn't available).
Pro adds AI Analysis on every report too, which is handy for spotting an FX line that's moving more than you'd expect. If your FX activity is significant, invite your bookkeeper or CPA to review the setup. See the Pro plan on US pricing and how bank reconciliation works.
FAQs
Is an FX loss a real loss?
A realized FX loss is real: you received fewer dollars than you recorded. An unrealized loss is a paper loss that can reverse if the rate moves back before the invoice or bill is settled.
Where do FX gains and losses go on the P&L?
Most small businesses show them as "other income" or "other expense," separate from operating revenue and costs, so they don't distort gross margin.
Should I revalue open invoices every month?
If you have meaningful foreign-currency balances and prepare accrual-basis financial statements, month-end revaluation gives a truer balance sheet. For a few small foreign invoices a year, many businesses only recognize the realized difference on payment. Ask your CPA what fits.
Why doesn't my foreign payment match the invoice even after FX?
Look for fees. Incoming wire fees, intermediary bank charges and payment platform fees often come out of the amount before it reaches you. Record them as bank fees.
Which exchange rate should I use?
Use a consistent, reliable source for the transaction date. What matters most is consistency: the same source and the same timing every month.
Track the currency, separate the fees, and the leftover difference is just the market doing what markets do.
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