LIFO stands for last in, first out. In practice, it means the most recently purchased inventory is the inventory your books treat as sold first, even if the physical unit that actually shipped to a customer was sitting on a shelf for six months.
That gap between the accounting assumption and the physical reality is the entire story of LIFO, and it’s exactly why the answer to the question in this headline is, for most ecommerce sellers, no. Not always, but usually. Let me walk through why, because the reasoning matters more than the conclusion.
What the LIFO Method Actually Does
Every inventory accounting method exists to answer one question: when you sell a unit, which cost do you assign to it? You bought units at different prices over time, prices rise and fall, and the method you choose determines which of those historical costs gets matched against the sale.
LIFO assumes the newest inventory, the last stock that came in, is the first stock that goes out the door. FIFO, its more common counterpart, assumes the opposite, the oldest inventory sells first. Weighted average cost sits in between, blending all costs together into one average figure per unit.
None of these methods need to match your actual physical fulfillment process. A warehouse can genuinely ship oldest stock first while the books are recorded under LIFO. The method is an accounting convention, not a shipping instruction, which is a distinction that trips up a lot of first time sellers.
The LIFO Formula
The core formula is straightforward once you see it applied:
Cost of Goods Sold (LIFO) = Cost of the most recently purchased units, applied in reverse chronological order until the quantity sold is fully accounted for
There’s no single algebraic equation the way there is for, say, calculating gross margin, because LIFO is a sequencing method rather than a single calculation. It’s easier to see through an example than to memorize as a formula.
A Worked Ecommerce Example
Say you run a small home goods store and you’ve made three separate purchases of the same ceramic mug over one quarter.
- January: 100 units at 4 dollars each
- March: 150 units at 5 dollars each
- June: 100 units at 6 dollars each
By the end of June, you’ve sold 180 units. Under LIFO, you assume those sales came from the most recent purchases first. That means all 100 units from June (at 6 dollars) and 80 of the 150 units from March (at 5 dollars) are treated as sold.
COGS under LIFO = (100 x 6) + (80 x 5) = 600 + 400 = 1,000 dollars
Your remaining ending inventory, on paper, consists of the 70 leftover March units and all 100 January units, the oldest and cheapest stock, still sitting on your balance sheet at the lowest cost basis.
Compare that to FIFO on the same numbers. Under FIFO, the January units go first, then March, meaning your COGS would be built from the cheaper early purchases: (100 x 4) + (80 x 5) = 400 + 400 = 800 dollars.
Same 180 units sold. Two different COGS figures, 1,000 dollars under LIFO versus 800 dollars under FIFO, purely because of which cost layer the accounting method assumes you consumed. That 200 dollar swing flows straight through to reported profit.
Why This Matters More Than It Looks
In a period of rising prices, LIFO produces a higher COGS and therefore a lower reported profit than FIFO, which in turn means a lower tax bill in that period. That’s the entire reason LIFO exists as a method, it was built for businesses holding large volumes of non perishable inventory during inflationary stretches, think steel, oil, industrial materials, where prices climb steadily and the tax deferral compounds meaningfully over years.
Ecommerce almost never looks like that. Most online sellers carry inventory that turns over relatively quickly, ranges across dozens or hundreds of SKUs, and often includes products where holding older stock too long is a liability rather than an advantage, whether that’s fashion going out of season or electronics losing relevance. The conditions that make LIFO genuinely valuable rarely exist in a typical ecommerce operation.
The Tax and Reporting Complications
There’s a second, less discussed problem. If you use LIFO for tax reporting in the United States, IRS conformity rules generally require you to also use LIFO for your financial statements, meaning you can’t show a rosier profit picture to investors or lenders while claiming a lower one to the IRS. That conformity requirement alone eliminates one of the reasons a larger company might otherwise consider it.
There’s also an international wrinkle worth knowing even if it doesn’t apply to you yet. LIFO is not permitted under IFRS, the accounting standard used across most of the world outside the US. Any ecommerce business planning to expand internationally, bring on international investors, or eventually get acquired by a company reporting under IFRS will likely need to unwind LIFO at some point, which is its own project.
And switching methods isn’t casual once you’ve picked one. The IRS requires filing Form 970 to adopt LIFO, and reversing that decision later typically requires formal approval rather than a simple internal policy change. This is not a setting you toggle back and forth based on which quarter looks better.
When LIFO Might Actually Make Sense
I don’t want to overstate the case against it. A business holding genuinely non-perishable, slow-turning inventory during a period of sustained cost inflation, alongside enough purchase volume for the tax deferral to be worth the added complexity, is the profile LIFO was built for. That’s a narrow slice of e-commerce, but it exists; certain durable goods sellers with long shelf lives and consistent, high-volume restocking come closest to fitting it.
For the overwhelming majority of Shopify stores, Amazon sellers, and multichannel operators, though, FIFO or weighted average cost tend to map far more naturally onto how the business actually operates, and they keep the books simpler to explain to a lender, an investor, or your own future self trying to make sense of last year’s numbers.
If you’re weighing this decision for your own store, our full inventory accounting methods comparison lays out FIFO, LIFO, and weighted average side by side. If the tax mechanics here feel like more than you want to untangle alone, that’s a reasonable point to bring in outside help rather than guess.
