Foreign-currency invoicing and exchange differences: bookkeeping for sales in another currency

Every business that sells or buys in a foreign currency actually deals with two separate uncertainties: first the price itself, and second the exchange rate changing between the day you issue the invoice and the day you collect the money. This second uncertainty — the exchange difference — is the pre-accounting topic that confuses most SMBs the most: "The rate changed, so how much do I invoice now, is there VAT, who invoices whom?"

In this guide we cover honestly how a foreign-currency invoice is issued, why the invoice should carry both the foreign-currency and the local-currency amount, how the exchange difference arises, how the exchange-difference invoice works in Turkey, and how to track all of this in the customer account. Note: this content is general information; regulations can change, so consult your accountant for situations specific to your business.

What is a foreign-currency invoice?

A foreign-currency invoice is one whose amount is stated in a foreign currency (dollars, euros, etc.). In Turkey it's possible to issue a foreign-currency invoice, but the invoice is expected to also show the local-currency (TRY) equivalent — this equivalent is calculated at the valid rate on the invoice date (usually the Central Bank rate). So even if the invoice is issued in a foreign currency, its equivalent is always also recorded in the local currency for accounting and tax.

The practical result: a foreign-currency invoice has two numbers — the amount in the contract's currency (for example, 1,000 USD) and the local-currency equivalent calculated at the invoice-date rate. Recording these two numbers and the rate used is the prerequisite for correctly calculating the exchange difference later.

How does the exchange difference arise?

1FX Invoice2TRY Equivalent (rate)3Collection (new rate)4Exchange Difference5Difference Invoice

The exchange difference arises from the rate change between the day you issue the invoice and the day you collect (or pay) the money. Say you issued a 1,000 USD invoice and the rate was at a certain level that day; if the rate has changed by the time you collect a month later, the local-currency amount you receive differs from the equivalent on the invoice day. That gap is the exchange difference. If the local currency depreciated and you're the foreign-currency creditor, the difference is in your favor; if it appreciated, against you.

This difference isn't just an accounting entry; it's a real income or expense item. That's why a business working in foreign currency has cash flow that depends not only on the sale amount but on the rate at collection time — a cash flow plan that ignores the rate is incomplete.

The exchange-difference invoice: who invoices whom?

In seller's favorIn buyer's favorThe party in whose favor it arises issues the difference invoice (+ VAT)Exchange Difference

When the exchange difference arises, the party in whose favor it arose issues an "exchange-difference invoice" to the other side. For example, if a difference arose in favor of the seller who is the foreign-currency creditor, the seller issues the exchange-difference invoice to the buyer. Conversely, if the difference favors the buyer, the buyer issues it to the seller. The amount of this invoice is the local-currency value of the exchange difference between the two dates.

An important point in Turkey: the exchange difference is subject to VAT. So the exchange-difference invoice calculates VAT at the rate the original transaction was subject to. This means it's wrong to treat the exchange difference as merely "the gap" and try to pass it without VAT. (Since regulatory details can change, it's healthiest to confirm current practice with your accountant.)

Which rate is used?

Choosing the right rate is the foundation of the exchange-difference calculation. In general practice, the Central Bank rate on the invoice date is used as the basis; the collection/payment day's rate is used on that day, and the difference between the two dates is calculated. What's critical is being consistent about which rate (buying or selling) and which date you use — using one rate today and a different logic tomorrow makes your customer account impossible to untangle. This consistency also eases the account reconciliation done later.

Period-end valuation

Your not-yet-collected foreign-currency receivables and unpaid foreign-currency payables are revalued at the period end (month/year end) at that day's rate. This valuation matters for seeing the real picture: the rate change raises or lowers the local-currency value of your open foreign-currency position even if no cash has moved yet. Being aware of this at the pre-accounting level ensures you don't get surprised when working with your accountant at period end.

Tracking foreign currency in the account

The most common mistake when working in foreign currency is keeping the account only in the local currency. The right approach is to track foreign-currency invoices in both the foreign currency and the local currency: how many dollars the customer owes you (the foreign-currency balance) and its current local-currency equivalent should be shown separately. That way you can answer both "how many dollars am I owed?" and "how much is that at today's rate?" at the same time. The foreign-currency version of account tracking is built on this dual-currency logic.

Invoice types and foreign currency

When working in foreign currency, document discipline also matters. The proforma invoice you give before a sale can be in a foreign currency, but it's not an official invoice; when the actual official invoice is issued, the local-currency equivalent also appears on the document. The same rule applies when issuing an e-invoice or e-archive: the foreign-currency amount and the local-currency equivalent are together. Getting the documents right from the start also eases the exchange-difference calculation later.

Exchange risk and pricing

The hidden cost of working in foreign currency is exchange risk: on long-term collections, if the rate turns against you, you can lose money on a sale you thought was profitable. There are a few ways to manage this — short collection terms, clearly stating in the contract how the exchange difference will be shared, or hedging with financial instruments. At the pre-accounting level, the most important thing is to accept that the rate is a cost item and give it a place in pricing and cash planning.

Common mistakes

• Omitting the local-currency equivalent on the invoice: Writing only the foreign-currency amount breaks both document discipline and the later exchange-difference calculation.
• Not recording the rate used: If you don't note the invoice-date rate, you can't correctly calculate the difference at collection.
• Passing the exchange difference without VAT: In Turkey the exchange difference is subject to VAT; skipping it creates tax risk.
• Keeping the account only in local currency: You lose the foreign-currency balance; "how many dollars am I owed?" goes unanswered.
• Inconsistent rate logic: Using the buying rate in one transaction and the selling rate in another makes reconciliation impossible.
• Ignoring exchange risk in pricing: On a long-term foreign-currency sale, if the rate turns against you your profit evaporates.

Getting-started checklist

• 1. Write the local-currency equivalent on every foreign-currency invoice. At the invoice-date rate.
• 2. Record the rate used and the date. This is the foundation of the exchange-difference calculation.
• 3. Keep the account in dual currency. Show both the foreign-currency and local-currency balance.
• 4. Calculate the exchange difference at collection. Find the difference between the two dates in local currency.
• 5. Issue the exchange-difference invoice with VAT. The party in whose favor it arose issues it.
• 6. Value the open position at period end. Avoid surprises with your accountant.

Frequently asked questions

Can I issue a foreign-currency invoice in Turkey?

Generally yes, you can issue the invoice in a foreign currency, but the local-currency equivalent must also be on the document. In some cases (especially certain contracts between parties resident in Turkey) there may be currency restrictions; it's best to consult your accountant for your own situation.

Is VAT applied to the exchange difference?

In Turkey the exchange difference is subject to VAT; the exchange-difference invoice includes VAT at the original transaction's rate. Since regulatory details may change over time, confirm current practice with your accountant.

Do I always have to issue an exchange-difference invoice?

When an exchange difference arises, the party in whose favor it arose is expected to issue a document. Practice may vary by the size of the amount and the nature of the transaction; following a systematic, consistent documentation approach is healthiest both legally and for account reconciliation.

How can a small business track this easily?

The key is recording the currency + amount + rate + date quartet on every foreign-currency transaction and keeping the account in dual currency. A pre-accounting/CRM tool that supports this greatly reduces the error risk of doing the exchange-difference calculation and reconciliation by hand.

Foreign-currency invoicing and exchange differences aren't as complex as they look; the real issue is discipline. Record the foreign-currency amount, the local-currency equivalent, the rate, and the date on every invoice; at collection, calculate the difference and have the favored party issue the VAT-inclusive exchange-difference invoice; keep the account in dual currency. When you do this systematically, exchange volatility stops being a nightmare and becomes a manageable, measurable item — and working with your accountant at period end gets much easier too.