IAS 21 answers a question that sounds simple until you try it: if a transaction happened in one currency and the accounts are presented in another, which exchange rate do you use? There are three candidate rates and three categories of balance, and the standard's difficulty is entirely in matching them correctly. Get the monetary/non-monetary split right and everything else falls out.
Functional Currency vs Presentation Currency
Functional currency is the currency of the primary economic environment in which the entity operates — the currency that mainly influences its selling prices and its labour and material costs. It is a matter of fact, determined by the circumstances, not a free choice.
Presentation currency is the currency in which the financial statements are presented. This is a free choice — an entity may present in any currency it likes.
Everything in IAS 21 flows from the functional currency. A transaction is "foreign" if it is denominated in anything other than the functional currency.
Initial Recognition
A foreign currency transaction is recorded on initial recognition by applying the spot exchange rate at the date of the transaction. For practical reasons, an average rate for a week or a month may be used if rates don't fluctuate significantly — but not if they do.
At the Reporting Date: The Monetary/Non-Monetary Split
This is the heart of the standard. At each reporting date:
Monetary items are translated at the closing rate. Monetary items are units of currency held, and assets and liabilities to be received or paid in a fixed or determinable number of currency units: cash, receivables, payables, loans.
Non-monetary items measured at historical cost are translated at the historical rate — the rate at the date of the transaction. They are not retranslated. Inventory at cost, property, plant and equipment, prepayments.
Non-monetary items measured at fair value are translated at the rate at the date the fair value was measured.
The test for monetary is the "fixed number of currency units" right to receive or obligation to pay. A receivable of €100,000 is monetary — you will receive exactly €100,000. A machine bought for €100,000 is not — you own a machine, not a claim to currency.
Worked Example: A Foreign Purchase
A company with a US dollar functional currency buys equipment from a European supplier for €200,000 on 1 November 2026, on credit. Year end is 31 December 2026, and the payable is settled on 28 February 2027.
Rates: 1 Nov — €1 = $1.10 | 31 Dec — €1 = $1.15 | 28 Feb — €1 = $1.08
1 November — initial recognition at the spot rate:
Dr Equipment — $220,000 (€200,000 × 1.10)
Cr Accounts Payable — $220,000
31 December — retranslate the monetary item only:
Payable at closing rate: €200,000 × 1.15 = $230,000
Previously recorded: $220,000
Exchange loss: $10,000
Dr Foreign Exchange Loss — $10,000
Cr Accounts Payable — $10,000
The equipment stays at $220,000. It is a non-monetary asset carried at historical cost and is never retranslated. This is the step students most often get wrong — retranslating the asset alongside the liability feels symmetrical and is incorrect.
28 February — settlement:
Cash paid: €200,000 × 1.08 = $216,000
Payable carried at: $230,000
Exchange gain: $14,000
Dr Accounts Payable — $230,000
Cr Cash — $216,000
Cr Foreign Exchange Gain — $14,000
Over the whole transaction the net effect on profit is a $4,000 gain, split across two periods — which is exactly the point of retranslating at each reporting date.
Where Exchange Differences Go
Exchange differences on monetary items are recognised in profit or loss in the period they arise. That is the general rule and covers the great majority of cases.
There is one significant exception. Exchange differences on a monetary item that forms part of a net investment in a foreign operation are recognised in other comprehensive income in the consolidated financial statements, and accumulated in a separate component of equity. They are reclassified to profit or loss on disposal of the foreign operation — one of the recycling OCI categories under IAS 1.
Where a gain or loss on a non-monetary item is itself recognised in OCI (a revalued property, say), any exchange component of that gain or loss follows it into OCI.
Translating a Foreign Operation for Consolidation
When a foreign operation's results are translated into the group's presentation currency:
- Assets and liabilities — at the closing rate at the reporting date
- Income and expenses — at the rates at the transaction dates (an average rate is commonly used as an approximation)
- All resulting exchange differences — recognised in OCI
Note that all assets translate at closing here, including non-monetary ones. This is a different exercise from translating foreign currency transactions, and conflating the two rules is a reliable source of lost marks.
Where Marks Are Usually Lost
- Retranslating non-monetary assets at the closing rate. Inventory at cost and PP&E stay at the historical rate, permanently.
- Confusing transaction translation with foreign operation translation. In the second, everything on the balance sheet moves to closing rate.
- Putting net investment exchange differences through profit or loss. They go to OCI and recycle on disposal.
- Getting the gain/loss direction backwards on a payable. If the foreign currency strengthens, a foreign currency payable costs more — that's a loss. A receivable is worth more — a gain.
- Forgetting to retranslate at the reporting date at all, and recognising the entire difference only on settlement.
- Treating a prepayment as monetary. A prepayment gives a right to goods or services, not to a fixed number of currency units.
The reliable way through an IAS 21 question is to label every balance monetary or non-monetary before writing a single rate down — the classification decides the rate, and the rate decides everything else. Accountely's foreign currency challenges score the classification and the resulting translation separately, so a single mislabelled balance doesn't cascade. For where the OCI half of this standard sits in the primary statements, see IAS 1 presentation of financial statements.