IFRS vs GAAP: Key Differences Explained

If you are studying financial reporting, the difference between IFRS and US GAAP comes up constantly — and it trips people up because the two frameworks often reach different answers for the same transaction. This guide explains what each one is, the key differences that actually matter, and why they show up in your exams. Most professional exams sat outside the US — including ACCA's financial reporting papers — are examined under IFRS, so knowing where US GAAP diverges is genuinely useful.

What is IFRS?

IFRS (International Financial Reporting Standards) is the set of accounting standards issued by the International Accounting Standards Board (IASB). It is used in well over 140 jurisdictions, including the UK, the EU, Australia and much of Asia and Africa. IFRS is described as principles-based: the standards set out the underlying objective and require professional judgement to apply it, rather than prescribing a detailed rule for every situation.

What is US GAAP?

US GAAP (Generally Accepted Accounting Principles) is the framework issued by the Financial Accounting Standards Board (FASB) and used by companies reporting in the United States. Compared with IFRS it is more rules-based — it tends to give specific, prescriptive guidance and bright-line thresholds, which can mean more detailed rules but less room for interpretation.

Principles vs rules: the core difference

Almost every specific difference flows from this one distinction. Because IFRS is principles-based, it leans on judgement and the economic substance of a transaction; because US GAAP is more rules-based, it provides detailed criteria to follow. Neither approach is automatically "right" — but it explains why the two frameworks can produce different numbers from identical facts.

Key differences between IFRS and US GAAP

Inventory: LIFO and write-down reversals

IFRS does not allow the last-in, first-out (LIFO) method, on the basis that it does not faithfully reflect how inventory actually moves. US GAAP still permits LIFO. The two also differ on write-downs: under IAS 2, if the net realisable value of previously written-down inventory recovers, the write-down is reversed up to the original cost — under US GAAP, an inventory write-down is permanent and cannot be reversed.

Development costs

Under IFRS (IAS 38), development costs are capitalised as an intangible asset once specific criteria are met — for example, technical feasibility and the probability of future economic benefits. Under US GAAP, development costs are generally expensed as incurred. The same project can therefore sit on the balance sheet under IFRS but hit the income statement under US GAAP.

Revaluation of assets

IFRS lets companies choose a revaluation model, carrying property, plant and equipment (and certain intangibles) at fair value. US GAAP generally sticks to historical cost and does not allow assets to be revalued upwards. This can lead to materially different asset values and depreciation charges between the two frameworks.

Why it matters for your exams

For most students outside the US, the practical answer is simple: you are examined under IFRS. ACCA's Financial Reporting (FR) and Strategic Business Reporting (SBR) papers, CIMA's reporting papers, and the standalone ACCA Diploma in IFRS (DipIFR) all test IFRS. Knowing where US GAAP diverges is mainly useful for context, for roles in US-listed groups, and for the occasional comparison question. When you study the individual standards — such as IFRS 15 on revenue recognition and IFRS 16 on leases — you are learning the IFRS treatment that your exam will assess.

Which framework is better?

Neither is objectively better — they suit different environments. IFRS's principles-based approach offers flexibility and global comparability across 140-plus jurisdictions; US GAAP's detailed rules offer consistency and less room for interpretation within the US market. The two boards have worked to converge several standards over the years (revenue and leases being notable examples), narrowing some — though not all — of the gaps.

Frequently asked questions

Is IFRS or US GAAP used in the UK?

UK-listed groups report under IFRS (UK-adopted IFRS). Many private UK companies instead use FRS 102, a UK GAAP standard based on IFRS principles but simplified for smaller entities.

What is the biggest difference between IFRS and US GAAP?

The overarching difference is principles-based (IFRS) versus rules-based (US GAAP). The most commonly cited specific differences are the prohibition of LIFO under IFRS, the capitalisation of development costs, the ability to reverse inventory write-downs, and the option to revalue assets.

Does my ACCA or CIMA exam test US GAAP?

No — ACCA and CIMA reporting papers are examined under IFRS. US GAAP differences are useful background rather than core examinable content.

Can a company use both IFRS and US GAAP?

A company reports under one framework, but groups with US-listed parents or subsidiaries often prepare a reconciliation between the two so figures can be compared across the group.

Build your financial reporting confidence

IFRS is the framework that underpins your exams and most reporting roles outside the US. Learnsignal's ACCA courses cover the standards in depth, with AI-adaptive practice and tutor support to help the differences actually stick. Explore the courses and build your reporting knowledge from the standards up.