Switching from FIFO to LIFO is prospective, not retrospective. You start applying LIFO at the beginning of the election year, your opening inventory that year becomes the base LIFO layer, and prior-period financial statements and tax returns are left alone. Nothing gets restated, and no cumulative-effect adjustment lands in retained earnings.
That answer holds for both sides of the ledger: GAAP financial reporting and federal income tax. The reasons differ, but the outcome is the same, and the mechanics of the election are simpler than most accounting method changes.
Why the Change Is Prospective
Under GAAP, a voluntary change in accounting principle usually requires retrospective treatment, with prior periods restated as if the new method had always been in place. Inventory changes involving LIFO are the major exception. Reconstructing historical LIFO layers and their costs after the fact is treated as impracticable, because the layer-by-layer data was never tracked. When retrospective application is impracticable, GAAP directs the company to apply the new method prospectively, starting from the beginning of the year of change.
The tax side reaches the same result through a different route. The IRS doesn’t reopen prior tax years when you adopt LIFO. A first-time LIFO election is a statutory election under IRC Section 472, not a method change that reaches back and reworks the past.1Office of the Law Revision Counsel. 26 USC 472 – Last-in, First-out Inventories Because the election applies from the start of the year you elect, there is no Section 481(a) cumulative catch-up to compute on the way in. Adoption is clean.
How to Make the Election
A first-time LIFO election is filed on Form 970, Application to Use LIFO Inventory Method, attached to your income tax return for the first year you want LIFO to apply.2Internal Revenue Service. About Form 970, Application to Use LIFO Inventory Method This is the point where people trip up: Form 3115 is not the right form for adopting LIFO. Form 3115 is the accounting method change application, and it comes into play when you leave LIFO or make certain other inventory changes. Going into LIFO for the first time is a Section 472 election, and Form 970 is the vehicle.
The return that carries Form 970 has to be timely filed, including extensions. Miss that window and you’ve missed the election year.
What Prospective Treatment Looks Like on Your Books
The mechanics are straightforward. Your beginning inventory for the first LIFO year is valued at cost, and that opening balance becomes your base LIFO layer. From that starting point forward, you track LIFO layers year by year. Nothing about the years before the election gets touched.
On the financial statement side, there is no cumulative-effect adjustment to retained earnings, no reclassification of prior income, and no restated comparatives. The opening inventory of the year of change simply becomes the initial LIFO layer, and the new method applies from that date onward. It’s one of the cleanest prospective treatments in accounting.
On the tax return, the same thing happens in reverse-engineered form. Because you’re beginning LIFO at the start of the election year and valuing that opening inventory at cost, there is no accumulated difference between an old method and a new method to true up. The election is the starting line.
The Conformity Requirement You’re Signing Up For
Adopting LIFO for tax means adopting LIFO for financial reporting. IRC Section 472(c) requires that if you use LIFO on your tax return, you must also use LIFO on any financial statements issued to shareholders, partners, beneficiaries, and creditors.1Office of the Law Revision Counsel. 26 USC 472 – Last-in, First-out Inventories The IRS enforces this strictly. Reporting FIFO earnings to investors while claiming LIFO on your return can result in the IRS disqualifying the LIFO election entirely.3Internal Revenue Service. LIFO Conformity
This conformity rule is unique to LIFO. FIFO, weighted average, and other inventory methods carry no such requirement. It’s worth understanding before you elect: you get LIFO everywhere or nowhere, and the higher earnings figure that FIFO would produce for investors is off the table once you make the switch.
Whether You Even Need to Elect
Not every business has to work through the LIFO decision. For taxable years beginning in 2026, businesses with average annual gross receipts of $32 million or less over the prior three tax years qualify as small business taxpayers under IRC Section 448(c).4Internal Revenue Service. Rev. Proc. 2025-32 That threshold is inflation-adjusted annually from a base of $25 million.5Office of the Law Revision Counsel. 26 USC 448 – Limitation on Use of Cash Method of Accounting
Small business taxpayers can use simplified inventory methods or treat inventory as non-incidental materials and supplies, which may take the FIFO-versus-LIFO question off the table entirely. Aggregation rules apply where related entities are involved, and tax shelters are excluded from the exemption regardless of receipts. If you’re comfortably under the threshold, a simplified method is often the easier path than committing to the conformity discipline that LIFO requires.
If You Later Reverse Course
One boundary worth flagging, because it’s the opposite of the clean prospective treatment on the way in: leaving LIFO does not work the same way. A change from LIFO to another method is treated as a change in accounting method, requires IRS consent through Form 3115,6Internal Revenue Service. About Form 3115, Application for Change in Accounting Method and triggers recapture of the accumulated LIFO reserve as a positive Section 481(a) adjustment. Financial statements are still not restated, but taxable income increases by the full reserve, spread ratably over four tax years starting with the year of change.7Internal Revenue Service. Rev. Proc. 2015-13 For years of LIFO use during rising costs, that reserve can be substantial. It’s a factor to weigh before adopting LIFO, because the exit is more complicated than the entry.