FIFO vs LIFO: What Actually Changes, and What Does Not

The goods do not move differently

The names are misleading. First-in-first-out and last-in-first-out sound like warehouse policies, and in a warehouse they would be — you rotate perishable stock so the oldest leaves first, and you take from the front of a bin because it is nearest. But as accounting terms they describe nothing physical. A supermarket that rotates its milk religiously can still report on LIFO, and a gravel merchant who genuinely sells the top of the pile first can report on FIFO. What the method chooses is which purchase cost gets attached to the units that left, and which cost stays on the balance sheet in the units that remain.

This matters because it settles a whole class of arguments before they start. Nobody has to defend LIFO as a description of how a stockroom works; it is not one. Both methods are simply ways of splitting a known total. In the worked example, $52,000 of purchases has to be divided between cost of sales and closing inventory, and the two numbers must always add back to $52,000. FIFO splits it $36,000 and $16,000. LIFO splits it $42,000 and $10,000. Weighted average splits it $39,000 and $13,000. Three different cuts of the same cake, and the cake is the same size in every case.

One year, worked both ways

Four purchases of 1,000 units each, at $10, $12, $14 and $16, total 4,000 units for $52,000 — an average cost of $13. Three thousand units sell at $25, so revenue is $75,000 and 1,000 units remain. Under FIFO the sale consumes the $10, $12 and $14 layers: 1,000 × 10 + 1,000 × 12 + 1,000 × 14 = $36,000, and the $16 layer survives as $16,000 of inventory. Under LIFO the sale consumes the $16, $14 and $12 layers: $42,000, and the original $10 layer survives as $10,000. Weighted average charges 3,000 × $13 = $39,000 and leaves $13,000.

Carry that down the income statement and the divergence widens on the way. Gross profit is $75,000 minus cost of sales: $39,000 under FIFO, $33,000 under LIFO, $36,000 on weighted average. Deduct $15,000 of operating expenses and profit before tax is $24,000, $18,000 and $21,000. Tax at 25% takes $6,000, $4,500 and $5,250, leaving a net profit of $18,000, $13,500 and $15,750. The gap between FIFO and LIFO is $6,000 of pre-tax profit and $4,500 of net profit, on a business whose trading was byte-for-byte identical. Anyone comparing two companies on net margin without checking their cost formula is comparing an accounting choice.

Cash before tax is identical, to the cent

This is the check that puts the whole comparison in proportion. The business received $75,000 from customers, paid $52,000 to suppliers and $15,000 in operating expenses. That is $8,000 of operating cash before tax, and it is $8,000 under FIFO, $8,000 under LIFO and $8,000 on weighted average, because none of those three transactions knows or cares which cost formula the accountant chose. Not a single euro or dollar moved differently. The cost formula rearranges how a fixed pile of spending is reported across two lines — one on the income statement, one on the balance sheet — and nothing else.

Then tax arrives, and it is real. FIFO owes $6,000, LIFO owes $4,500. After the tax payment the business holds $2,000 under FIFO and $3,500 under LIFO — a genuine $1,500 difference in the bank, produced by nothing but the choice of formula. That single number is the entire economic case for LIFO in a jurisdiction that allows it: an interest-free deferral of tax for as long as prices keep rising and the inventory layers stay buried. It is not a saving. It is a postponement, and section six explains when the bill arrives.

The LIFO reserve, and what it is for

A company reporting on LIFO carries inventory at old costs, which after a few years of inflation can be badly out of date. The LIFO reserve is the bridge: the difference between what inventory would be worth under FIFO and what it is carried at under LIFO. In the worked example it is $16,000 − $10,000 = $6,000, which is exactly the cumulative difference in cost of sales the two methods have reported. That is not a coincidence — the reserve is the running total of every euro of profit LIFO has deferred since the layers were laid down.

That is why the disclosure exists. Add the reserve back to the LIFO inventory figure and you recover the FIFO figure — $10,000 + $6,000 = $16,000 — which lets an analyst restate a LIFO company onto a comparable basis before putting it beside a FIFO or IFRS-reporting peer. The reserve also carries a deferred tax liability: at 25%, the $6,000 implies $1,500 of tax that has been postponed rather than avoided. A rising reserve means the deferral is still growing. A falling reserve is a warning that some of it is being paid back.

What the standards actually permit

Under IFRS the question is closed. IAS 2 Inventories requires the cost of interchangeable items to be assigned using first-in-first-out or weighted average cost; LIFO was removed as a permitted treatment in the 2003 revision of the standard, on the reasoning that it does not faithfully represent inventory flows. A company reporting under IFRS therefore has no LIFO option at all, which is why the debate is invisible across most of Europe, and why the fr, es, pt, de and it readers of this article will meet LIFO mainly in translated American filings.

US GAAP is the other case. Topic 330 of the FASB codification still permits LIFO, and a substantial minority of large US filers use it for exactly the tax reason set out above. American tax law then adds a twist that has no equivalent elsewhere: the LIFO conformity rule in section 472(c) of the Internal Revenue Code says that a taxpayer using LIFO on its return must also use LIFO in the financial statements it gives to shareholders and creditors. You cannot take the lower tax and report the higher profit. That is why LIFO users disclose the reserve — it is the permitted way to tell investors what FIFO would have looked like without breaking conformity.

LIFO liquidation: the deferral comes back

Suppose the following year the business sells its remaining 1,000 units at $25 and buys nothing — a destocking year, which happens in every downturn and every supply squeeze. Under FIFO the units carry the $16 cost, so cost of sales is $16,000 and gross profit is $9,000. Under LIFO the only layer left is the original $10 one, so cost of sales is $10,000 and gross profit is $15,000. LIFO now reports the higher profit, and the higher tax with it. The old, cheap layer has surfaced, and the deferred profit has to be recognised all at once.

Add the two years together and the illusion dissolves. FIFO reports $39,000 then $9,000; LIFO reports $33,000 then $15,000. Both total $48,000. Over the full life of a batch of inventory the cost formula changes nothing at all — every euro of cost eventually passes through cost of sales, and the only question was in which year. That is the honest summary of the whole comparison: FIFO and LIFO redistribute profit and tax across periods, they do not create or destroy either, and the value of the difference is the value of holding money for a while rather than paying it away.

Frequently asked questions

Does the choice between FIFO and LIFO change how much cash the business has?

Only through tax. Operating cash before tax is identical — $75,000 collected, $52,000 paid to suppliers, $15,000 of expenses, so $8,000 under either method. The tax bill differs: $6,000 under FIFO against $4,500 under LIFO, so LIFO leaves $1,500 more in the bank. Everything else you see moving — cost of sales, inventory, gross profit, net profit — is presentation, not money.

Is LIFO allowed under IFRS?

No. IAS 2 Inventories allows only first-in-first-out or weighted average cost for interchangeable items, with specific identification for items that are not interchangeable. LIFO was withdrawn as a permitted treatment in the 2003 revision of the standard. US GAAP is different: Topic 330 of the FASB codification still permits LIFO, and US taxpayers who elect it are additionally bound by the LIFO conformity rule to use it in their published accounts as well.

What is the LIFO reserve and where do I find it?

It is the difference between what inventory would be worth on FIFO and its carrying amount on LIFO, disclosed in the inventory note of a LIFO filer's accounts. In the worked example it is $16,000 − $10,000 = $6,000, which equals the cumulative extra cost of sales LIFO has charged. Add it back to LIFO inventory to restate a company onto a comparable basis, and multiply it by the tax rate — here $1,500 — to see how much tax has been deferred rather than saved.

What happens to LIFO when prices fall?

The advantage inverts. LIFO charges the most recent costs to cost of sales, so when the newest purchases are the cheapest, LIFO reports the lower cost of sales, the higher profit and the higher tax — the exact opposite of the rising-price case. Everything in this article about LIFO reporting less profit assumes prices are going up. The same reversal happens without any price move at all if you sell down old layers: that is the LIFO liquidation described above, where the cheap historic cost surfaces and profit spikes.

Can I just switch methods when it suits me?

No. Both IFRS and US GAAP require a cost formula to be applied consistently to inventories of similar nature and use, and a change is treated as a change in accounting policy that must be justified and generally applied retrospectively. In the United States a change into or out of LIFO also needs the tax authority's consent and can trigger an immediate charge. Choose the formula on the economics of your inventory, not on this year's result, because you will be living with it.