How to Process Supplier Invoices in Foreign Currencies

Key terms: base currency, transaction currency and FX differences

Your base (functional) currency is the one your books are kept in; the transaction currency is the one on the invoice; and the FX difference is what changes between the two over time.

Term	Meaning	Example
Base currency	The currency your general ledger and financial statements are kept in	USD for a US company
Transaction currency	The currency the supplier invoices in and expects to be paid in	EUR from a German supplier
Spot rate	The exchange rate on a given date, used to record the invoice	EUR/USD on the invoice date
Unrealized FX gain or loss	The change in value of an unpaid invoice at a period-end remeasurement	Booked at month-end, adjusted later
Realized FX gain or loss	The final difference when the invoice is paid	Booked on the payment date

Step-by-step: processing a foreign-currency invoice

Capture the currency, translate at the invoice-date rate, match in the original currency, remeasure at month-end and settle in the invoice currency.

1
Step 1
Capture the invoice in the currency the supplier billed, and record the currency code (EUR, GBP, CAD) as well as the amount.
2
Step 2
Translate the invoice into your base currency at the exchange rate for the invoice date, from one documented rate source.
3
Step 3
Match and approve the invoice in its original currency, so price and quantity checks against the PO compare like with like.
4
Step 4
At each month-end, remeasure unpaid foreign-currency invoices at the closing rate and book the unrealized gain or loss.
5
Step 5
Pay the supplier in the invoice currency, and book the realized gain or loss between the carrying amount and what the payment cost in base currency.
6
Step 6
Reconcile the foreign-currency payables balance in both the original currency and the base currency at period end.

Exact requirements depend on your accounting framework (for example ASC 830 under US GAAP or IAS 21 under IFRS). Agree the rate source and remeasurement policy with your accountant or auditor.

Worked example: a €10,000 invoice for a US company

In this example, a €10,000 invoice is booked at $11,000, remeasured at month-end and paid for $10,900, for a net exchange gain of $100.

Example: €10,000 invoice from a German supplier, base currency USD
Date	Event	EUR/USD rate	USD value	FX entry
Sep 10	Invoice recorded	1.10	$11,000	None
Sep 30	Month-end remeasurement	1.12	$11,200	Unrealized loss $200
Oct 15	Paid in EUR	1.09	$10,900	Realized gain $300

Illustrative rates. Across both periods the net effect is a $100 gain: the invoice was booked at $11,000 and cost $10,900 to pay. The supplier receives exactly €10,000 either way.

Choosing an exchange-rate source

Use one source consistently, record the rate and date on each invoice, and have a documented way to override a rate when your bank or contract uses a different one.

Central bank reference rates. The European Central Bank publishes euro reference rates for 29 currencies around 16:00 CET each working day, and says they are for information purposes only (ECB). Many companies still use them for bookkeeping.
Commercial rate feeds. Data providers publish daily or intraday rates for more currencies.
Your accounting system's rates. QuickBooks Online and Xero supply daily rates when multi-currency is on.
Contract or bank rates. If a contract fixes the rate, or you buy currency forward, record that rate as an override and keep the evidence.

Common mistakes and controls

Most foreign-currency errors come from assuming the currency, mixing rate sources, and treating exchange movements as price variances.

Assuming “$” means US dollars. Canadian, Australian, Singapore and other dollars use the same symbol. Look for the currency code or a prefix such as C$ or A$.
Converting before matching. Comparing a EUR invoice with a USD-converted PO turns rate movements into false price variances.
Mixed rate sources. Different people pulling rates from different websites makes results impossible to reproduce for audit.
Paying in the wrong currency. The supplier receives less than invoiced and the shortfall reappears on the next statement.
Skipping month-end remeasurement. Large unpaid foreign-currency balances misstate liabilities if they stay at the original rate.

How Aequo AP handles foreign-currency invoices

Aequo AP detects the currency printed on each invoice during capture, and when the invoice is approved it records the base-currency amount using the exchange rate for the invoice date.

Currency detection. Each invoice is tagged with its ISO currency code. An explicit code on the invoice wins; prefixed symbols such as C$ and A$ are recognized; a bare “$” is treated as US dollars. Invoices showing more than one currency are flagged for review rather than guessed.
Base-currency conversion at approval. On approval, Aequo AP converts the invoice to your base currency at the rate for the invoice date from a daily exchange-rate feed, and stores the rate, rate date and rate source with the invoice. If no rate is available, the approval does not go through, so no invoice is approved without a base-currency amount.
Manual rate overrides. Upload a CSV of rates (date, currency, rate) to override the feed, for example to use your bank's rates. Overrides take precedence and can be removed to fall back to the feed.
Base currency by entity. Set the base currency for each legal entity in the FX settings.

Approved bills sync to QuickBooks Online, Xero, FreshBooks or Zoho Books, where multi-currency must be enabled to hold bills in the supplier's currency. See invoice matching in Aequo AP.

Frequently asked questions

Which exchange rate should I use for a supplier invoice?

Generally the rate on the date the transaction is recognized, usually the invoice date, from a consistent source. Many companies use a daily rate feed or a central bank reference rate, and some use a monthly average rate where it is a reasonable approximation. Document the policy and apply it the same way every time.

Should I pay a foreign supplier in their currency or mine?

Pay in the currency on the invoice unless the supplier agrees otherwise. Paying in your own currency moves the exchange decision to the supplier’s bank, which may charge for conversion and leave a short payment on their books that comes back as a statement difference.

What is a realized vs unrealized FX gain or loss?

An unrealized gain or loss is the change in value of an unpaid foreign-currency invoice when you remeasure it at month-end. A realized gain or loss is the final difference when you pay it, between the amount carried in your books and what the payment actually cost in your base currency.

Do I need multi-currency turned on in my accounting system?

Yes, if you want to record bills in the supplier’s currency. QuickBooks Online, Xero and most other systems require multi-currency to be enabled, and in QuickBooks Online it cannot be turned off again once enabled. Check your system’s rules before switching it on.

How do I three-way match a foreign-currency invoice?

Raise the purchase order in the supplier’s currency and match the invoice to it in that currency. Converting both to your base currency at different dates creates price variances that are really exchange-rate movements.

Automate matching, approvals and exception handling

Aequo AP captures invoices, matches them to purchase orders and receipts, routes approvals and flags duplicates and exceptions, then syncs with QuickBooks Online, Xero, FreshBooks or Zoho Books.

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Sources

Checked on October 23, 2026. Vendor capabilities and prices change; confirm current details with each vendor.

European Central Bank, Euro foreign exchange reference rates — published around 16:00 CET each working day for 29 currencies against the euro; for information purposes only