LIFO vs FIFO: GAAP and IFRS Treatment Explained
I had a trainee ask me last month why the inventory valuation on a client's financial statements looked completely different from what she expected, even though the physical stock count matched. It took me a minute to realize what had happened. She had learned inventory costing from a textbook that used IFRS examples, and this particular client, a US-based manufacturer, was reporting under US GAAP using LIFO. The numbers weren't wrong. They were just built on an assumption she hadn't been told wasn't universal.
That mix-up is more common than people expect, because LIFO and FIFO aren't just two calculation methods sitting side by side. One of them isn't even legal under IFRS, and that single difference cascades into everything from reported profit to tax bills to how comparable a US company's numbers are to a European one.
Quick answer: LIFO vs FIFO under GAAP and IFRS
FIFO (first-in-first-out) assumes the oldest inventory is sold first and is permitted under both US GAAP and IFRS. LIFO (last-in-first-out) assumes the newest inventory is sold first and is permitted under US GAAP but explicitly prohibited under IFRS (IAS 2). If you're comparing financial statements across the two frameworks, this single rule is often the biggest source of distortion in reported inventory values and cost of goods sold.
Why IFRS doesn't allow LIFO
Under IAS 2, the International Accounting Standards Board decided that LIFO doesn't faithfully represent how inventory actually moves through most businesses. In reality, most companies sell or use their oldest stock first, especially anything perishable or subject to obsolescence. LIFO assumes the opposite, and the IASB concluded that reporting it as if it reflected real inventory flow was misleading. So under IAS 2, companies can only use FIFO, weighted average cost, or specific identification for interchangeable inventory.
Under US GAAP, ASC 330 still permits LIFO alongside FIFO and weighted average. The reason it survives in the US comes down to tax, not accounting theory. During periods of rising prices, LIFO matches the newest, most expensive inventory costs against revenue, which produces a higher cost of goods sold, lower reported profit, and a smaller tax bill. There's a catch that trips people up here too. If a company uses LIFO for its tax return, it's required under what's called the LIFO conformity rule to also use LIFO for its financial reporting. You can't use LIFO to save on taxes and then report a rosier picture to investors using FIFO.
GAAP vs IFRS: Inventory Valuation at a Glance
| Aspect | US GAAP (ASC 330) | IFRS (IAS 2) |
|---|---|---|
| FIFO | Permitted | Permitted |
| LIFO | Permitted | Prohibited |
| Weighted Average | Permitted | Permitted |
| Write-down basis | Lower of cost or market | Lower of cost or net realizable value |
| Write-down reversal | Not permitted (permanent) | Permitted if value recovers |
How this actually changes the numbers
Say a company buys inventory in three batches at rising prices, and only sells enough to draw from the two most recent batches.
Under FIFO, the cost of goods sold is calculated from the oldest, cheapest inventory first, which produces a lower COGS and a higher reported gross profit. The ending inventory on the balance sheet reflects more recent, higher prices, so it tends to look closer to current replacement cost.
Under LIFO, the cost of goods sold is calculated from the most recent, most expensive purchases first, producing a higher COGS and lower reported gross profit. The ending inventory left on the balance sheet is made up of the oldest cost layers, which in an inflationary environment can end up significantly understated relative to what it would actually cost to replace that stock today.
Neither number is wrong. They're both accurate representations of a cost flow assumption, not a physical tracking of which units left the warehouse. That's the part I try to get across to trainees early, because it's easy to assume LIFO or FIFO describes the actual movement of goods rather than just how costs are assigned to the income statement and balance sheet.
Write-downs are another quiet difference
Beyond the LIFO question, the two frameworks also disagree on how to handle inventory that's lost value. Under US GAAP, inventory is written down using the lower of cost or market rule, and once that write-down happens, it's permanent. Even if the market value recovers later, you can't reverse it.
Under IFRS, inventory is written down to the lower of cost or net realizable value, and if the value genuinely recovers in a later period, the write-down can be reversed, up to the original cost. This is a smaller detail than the LIFO question, but it's one that catches people off guard when they're reconciling US GAAP and IFRS inventory balances that should theoretically be close but aren't.
What this means in practice
If you're a US business, the choice between LIFO and FIFO isn't just an accounting preference. It's a tax decision with real cash flow consequences during inflationary periods, and it locks you into the conformity requirement once you choose LIFO for tax purposes. If you're comparing your numbers to a company reporting under IFRS, whether for benchmarking, a potential acquisition, or investor reporting, remember that a LIFO reserve disclosure exists precisely so analysts can adjust LIFO-based numbers back to something closer to a FIFO equivalent for comparison.
If you're preparing financial statements under IFRS, this decision is already made for you. Weighted average or FIFO are your only options for interchangeable inventory, and that consistency is actually one of the reasons IFRS-reporting companies are easier to compare against each other across borders.
This is closely related to a question I get often around balance sheet classification. If you're also unsure whether certain costs sit as current or non-current, I've covered similar classification questions for right-of-use assets and for prepaid expenses under both frameworks.
Frequently Asked Questions
Is LIFO allowed under IFRS?
No. IAS 2 explicitly prohibits LIFO. Companies reporting under IFRS must use FIFO, weighted average cost, or specific identification for interchangeable inventory.
Why do US companies still use LIFO?
Mainly for tax reasons. During inflationary periods, LIFO produces a higher cost of goods sold and lower taxable income, improving cash flow. The trade-off is the LIFO conformity rule, which requires the same method to be used for financial reporting.
Can a company switch between LIFO and FIFO freely?
No. Changing inventory costing methods is considered a change in accounting principle and generally requires justification and consistent application going forward, not a year-to-year choice based on which produces better results.
The mistake I see most often isn't picking the wrong method. It's forgetting that the method itself changes what the numbers mean, and applying assumptions from one framework while reading statements prepared under the other. If you found this useful, you might also want to compare how prepaid and accrued expenses are treated differently under GAAP and IFRS.