For most U.S. businesses in a normal, inflationary pricing environment, LIFO is better for taxes than FIFO because it pushes the newest, highest inventory costs into Cost of Goods Sold and defers income tax. That answer flips when prices fall, and it comes with compliance rules and a liquidation risk that can erase the savings. Whether LIFO or FIFO is better for taxes ultimately depends on where your input costs are heading, how much inventory you carry, and whether you can live with the strings attached to a LIFO election.
How Each Method Moves Your Tax Bill
FIFO assumes the oldest inventory sells first. When prices are rising, that means the cheapest costs flow into Cost of Goods Sold and the more expensive recent purchases sit on the balance sheet. Lower expense, higher reported profit, higher tax.
LIFO reverses that. The most recently purchased inventory is treated as sold first, so today’s higher costs hit the income statement now. Cost of Goods Sold goes up, taxable income goes down, and ending inventory stays parked at older, lower prices. The cumulative gap between what inventory would be worth under FIFO and what it’s carried at under LIFO is called the LIFO reserve, and it represents income the business has deferred.
When LIFO Wins
Inflation is what makes LIFO work. As long as your replacement costs keep climbing, LIFO keeps feeding those higher costs into current expense and shrinking taxable income each year. The savings are technically a deferral rather than a permanent reduction, since total lifetime income under both methods would theoretically even out. In practice that rarely matters. A dollar of tax deferred is worth more than a dollar paid today, and the retained cash can be reinvested or used for working capital. At the 21 percent corporate rate, even a modest annual deferral compounds into real money.
The businesses that benefit most tend to carry large physical inventories exposed to persistent cost inflation. Automobile dealers, petroleum companies, and large retailers are among the most prominent LIFO users. If you buy and resell goods whose costs reliably climb year over year, you’re a natural candidate.
When FIFO Wins
LIFO’s advantage disappears, and reverses, when purchase prices fall. In deflation the newest inventory is the cheapest, so LIFO would assign those low costs to Cost of Goods Sold, shrinking the expense and raising the tax bill. FIFO would do the opposite, pulling older, higher costs into expense and cutting taxable income.
Sustained deflation across a whole inventory is uncommon in the U.S., but it happens in specific categories. Technology and consumer electronics see regular secular price declines. A business whose main inventory items keep getting cheaper may genuinely save on taxes with FIFO.
FIFO also wins on simplicity when the LIFO deferral would be trivial. If your inventory turns over very fast, if purchase prices barely move, or if you carry very little physical stock, the compliance costs of running LIFO can outweigh the tax savings. Startups with limited inventory and service businesses with minimal goods usually have no reason to bother.
The Conformity Rule That Comes With LIFO
The biggest string attached to LIFO is the conformity rule. If you elect LIFO for federal tax purposes, you must also use LIFO as the primary inventory method in financial reports issued to shareholders, partners, beneficiaries, and creditors.1Office of the Law Revision Counsel. 26 U.S. Code 472 – Last-in, First-out Inventories The rule exists to stop companies from showing low income to the IRS while showing high income to investors.
Break it and the IRS can terminate the LIFO election retroactively, forcing recalculation of past returns under FIFO with underpayment penalties and interest stretching back to the year you first adopted LIFO.1Office of the Law Revision Counsel. 26 U.S. Code 472 – Last-in, First-out Inventories Limited disclosure is allowed: you can show what inventory would be worth under FIFO in a footnote or parenthetical, and most LIFO users do exactly that so investors can read the LIFO reserve.
One boundary worth flagging: International Financial Reporting Standards prohibit LIFO. A company reporting under both U.S. GAAP and IFRS often ends up on FIFO globally to keep a single accounting system, giving up the U.S. tax savings rather than running dual books.
The LIFO Liquidation Problem
Every year a LIFO business adds inventory, it stacks up a new cost layer at that year’s prices. Over decades, the oldest layers can sit at prices from many years ago. As long as inventory levels hold or grow, those cheap layers stay untouched and the deferred tax stays deferred.
The trouble arrives when inventory drops below those historical layers. Selling into the old layers finally pushes those low costs into Cost of Goods Sold, but they barely dent current revenue, so taxable income spikes. That’s LIFO liquidation, and it can hit hard in a year the business may already be squeezed by the same supply issues that caused the drawdown.
Congress provides narrow relief for involuntary liquidations caused by specific events like energy supply disruptions, embargoes, or major foreign trade interruptions, but only after the Secretary of the Treasury publishes a notice identifying the affected goods and taxpayers.2Office of the Law Revision Counsel. 26 USC 473 – Qualified Liquidations of LIFO Inventories Outside those situations there is no safety valve. Anyone on LIFO has to manage stock levels carefully and keep a buffer to avoid triggering a liquidation by accident.
Electing LIFO or Switching Later
A business choosing LIFO for the first time files IRS Form 970 with the return for the year the election takes effect.3Internal Revenue Service. Form 970 – Application to Use LIFO Inventory Method The form asks for a description of the covered inventory, the prior valuation method, the unit of measure, and the pooling approach. An alternative election statement carrying the same information also works. No IRS National Office permission is needed for the initial election, and opening inventory for the year of change simply becomes the base-year layer at its existing cost.
Most electors use dollar-value LIFO rather than tracking individual units. Dollar-value LIFO groups related inventory into pools and measures changes in total dollar value using a price index.4Internal Revenue Service. Introduction to Dollar Value LIFO Items can enter and leave a pool without breaking the calculation, which makes it far more practical for businesses carrying hundreds of SKUs.
Switching methods later is a different exercise. Any change from one inventory method to another after the initial election requires IRS consent through Form 3115, Application for Change in Accounting Method.5Internal Revenue Service. About Form 3115 – Application for Change in Accounting Method6Internal Revenue Service. Changes in Accounting Periods and Methods of Accounting7Internal Revenue Service. Instructions for Form 3115
Any method change triggers a Section 481(a) adjustment so no income gets counted twice and nothing gets missed.8Office of the Law Revision Counsel. 26 U.S. Code 481 – Adjustments Required by Changes in Method of Accounting Switching from LIFO to FIFO almost always produces a positive adjustment: the entire LIFO reserve you built up gets added back to income. Under standard automatic consent, a positive adjustment is spread ratably over four tax years. A negative adjustment is taken all in the year of change. Those spreads reverse if the IRS forces the change during an examination, in which case the full adjustment hits in a single year.9Internal Revenue Service. 4.11.6 Changes in Accounting Methods Voluntary compliance is materially cheaper than getting caught.
You May Not Need Either Method
Plenty of businesses don’t have to pick between LIFO and FIFO at all. Small businesses that meet a gross receipts test are exempt from the general inventory accounting rules and can use a simplified approach instead.10Office of the Law Revision Counsel. 26 U.S. Code 471 – General Rule for Inventories The threshold uses average annual gross receipts over the three prior tax years. For 2023 it was $29 million, and it adjusts annually for inflation.11Internal Revenue Service. Threshold for the Gross Receipts Test Increased to $29 Million for 2023
A qualifying business can treat inventory as non-incidental materials and supplies, deducting costs when items are used or consumed rather than tracking each item through a formal inventory system. That sidesteps LIFO, FIFO, and their compliance costs entirely. Businesses currently on a formal system that want to switch file Form 3115 to make the change. The same threshold also exempts you from the Section 263A uniform capitalization rules, which otherwise force certain indirect costs like warehousing into inventory value. Dropping below the threshold clears both layers of complexity at once.
How to Decide
Start with the direction of your input costs. If they’re rising steadily and you plan to hold or grow inventory, LIFO’s deferral compounds year after year and usually wins the tax comparison. If your costs are flat, falling, or your inventory is small and fast-moving, FIFO is simpler and often produces a similar or better result. Then weigh what LIFO costs you in compliance: the conformity rule that binds your financial statements, the risk of a liquidation event turning years of deferral into one year’s income, and the complexity of maintaining pools and indices under dollar-value LIFO. If any of those risks are hard to manage, or if you report under IFRS abroad, FIFO can be the better answer even when the raw math favors LIFO. And if your gross receipts fall under the small-business threshold, the cleanest answer may be neither.