Functional Currency

Summary

Functional currency is not house jargon: it is a term of art defined by international accounting standards – IAS 21, The Effects of Changes in Foreign Exchange Rates and its US GAAP counterpart, ASC 830 (originally SFAS 52) – as "the currency of the primary economic environment in which the entity operates" (see Wikipedia: Functional currency for an accessible overview). This note follows that external definition and applies it at book level: the functional currency is the accounting currency of a book, or more precisely of the accounting entity and legal jurisdiction the book belongs to – the currency in which that book's P&L and Balance Sheet are expressed in the ledger. Every ledger book carries exactly one, because the legal jurisdiction a book belongs to mandates a reporting currency of its own – a UK-domiciled book must submit accounts in GBP regardless of what currencies its trades are actually denominated in – which forces every non-functional-currency position to be periodically converted, with the resulting movement booked as a distinct adjustment rather than silently absorbed. This is one of several distinct currency roles a book or trade carries at once; see Currency for how it relates to the others.

Detail

The currency of the ledger's own books

A book's functional currency is set by the currency of the accounting book to which it reports its financial statements, which is in turn dictated by the legal jurisdiction that book belongs to: an entity domiciled in the UK must submit its accounts in GBP, one domiciled in the US in USD, and so on, independent of which currencies the book's underlying trades happen to be denominated in. This is why a book's functional currency is not a free per-book choice but a consequence of where, legally, that book's records are reported – see Book and the ledger for the fuller accounting hierarchy a book sits within, and Business Unit for the organisational placement that ultimately determines it.

Converting non-functional-currency positions

Because trades happen in whatever currency the market quotes them in – their transactional currency – every non-functional-currency position a book holds must be periodically translated into functional currency for accounting purposes. A Functional Currency Balance is precisely this: a transactional-currency balance translated into the book's functional currency, typically using the London Closing Rate or another Close-of-Business rate determined by Head of Treasury – itself anchored to a particular business centre's own end-of-day cut-off, not a single global moment shared by every book. The daily, automated mechanism that performs this translation is the Ledger Sweep, documented there in full; the P&L movement the translation itself generates is booked as a distinct entry rather than blended into trading P&L, since it arises from currency translation rather than from any new economic event.

Facility and utilisation currency

A Facility Currency is the currency in which a functional-currency lending limit is set for a given entity; the corresponding Utilisation Currency is the currency, or currencies, in which that facility is actually drawn down. The two need not coincide: a facility denominated in one functional currency can, in practice, be utilised in whatever currency the borrowing actually takes place in, which is why utilisation is tracked as its own field rather than assumed to equal the facility's own currency.