The first time an Australian company incorporates a US subsidiary, someone in finance discovers AASB 121 the hard way — usually during an audit, usually after two years of translating everything at whatever rate was convenient.
AASB 121 is Australia's adoption of IAS 21. It governs how you translate foreign currency transactions and how you translate a foreign operation into your group's presentation currency. It is not complicated in principle. It is easy to get subtly wrong in practice, and the errors compound.
Everything depends on this, and it is a judgement rather than a choice. An entity's functional currency is the currency of the primary economic environment in which it operates — broadly, the currency that mainly influences its selling prices and its labour and material costs.
A US subsidiary with US customers, US staff and USD pricing has USD as its functional currency, regardless of what the Australian parent would prefer. A US-incorporated entity that only holds IP and is funded entirely by the Australian parent may well have AUD as its functional currency.
Getting this wrong invalidates everything downstream, so it is worth documenting the reasoning at the time rather than assuming.
People conflate these, and they are not the same thing.
Translating foreign currency transactions within an entity. Your Australian entity invoices a customer in USD. That transaction is recorded at the spot rate on the transaction date. At period end, the outstanding receivable — a monetary item — is retranslated at the closing rate, and the difference goes to profit or loss as a foreign exchange gain or loss.
Translating a foreign operation into the group's presentation currency. This is the consolidation exercise, and the rules differ.
When translating a subsidiary whose functional currency differs from the presentation currency:
That last point matters. The translation difference does not hit profit or loss. It sits in reserves until the foreign operation is disposed of, at which point the accumulated amount is reclassified to profit or loss.
Using one rate for everything. This is the most common error by a wide margin. The team translates the full trial balance at the month-end rate because that is what the spreadsheet does. The balance sheet is then roughly right and the P&L is wrong, and the two do not reconcile without a plug.
Putting translation differences through the P&L. Transaction gains and losses go to P&L. Translation of a foreign operation goes to OCI. Mixing them overstates or understates earnings, and it is exactly the sort of thing that draws attention in a due diligence.
No historical rate tracking on equity. Share capital and pre-acquisition reserves stay at historical rates. Systems that only store one rate per period cannot do this, so it gets approximated — and the approximation grows.
Intercompany balances translated inconsistently. If the parent translates a loan receivable at one rate and the subsidiary translates the matching payable at another, the intercompany balance will not eliminate. This is a very common source of consolidation differences.
The plug account. If your consolidation has an account whose purpose is to make the balance sheet balance, you have an FX treatment problem you have not diagnosed.
None of this is impossible in a spreadsheet. It is just fragile.
Doing it properly requires storing, for every transaction, the original currency amount, the entity's functional currency amount and the rate used — then applying different rate types to different account classes at consolidation, and tracking historical rates on equity indefinitely.
A ledger built for multi-currency at the data layer does this by construction. A ledger that stores one amount per transaction cannot, and the difference is absorbed by whoever maintains the consolidation workbook.
The same applies to intercompany elimination: if both sides of a related-party transaction are created from a single event, they translate consistently and eliminate cleanly.
Ask for three things from your current process: the functional currency determination for each entity and the reasoning behind it, the rate type applied to each class of account at consolidation, and the movement in the translation reserve for the last twelve months with an explanation.
If any of those cannot be produced quickly, it is worth resolving before your next audit rather than during it.
FX treatment is one of the areas where migrating to a modern platform tends to surface historical problems rather than create them. We work through this during planning, with your auditor involved, so the transition is a decision rather than a discovery.
If you have an ANZ-headquartered group with offshore entities, we are happy to review the treatment. More on how we run implementations.