Understanding First In First Out (FIFO) and LIFO Strategies for Stock Sales

When you decide to sell some of your stock holdings, you face a choice that’s often overlooked but can significantly impact your tax bill. The method you select for which shares to sell—whether you use FIFO or LIFO—can make the difference between keeping more of your profits or handing more money to the IRS.

What First In First Out (FIFO) Really Means for Your Shares

First in first out, commonly abbreviated as FIFO, is an investment accounting method that’s simpler than it sounds. When you sell stock using FIFO, you’re selling the shares you purchased earliest, regardless of their current value. If you bought 100 shares in 2020 and another 100 shares in 2025, and you now sell 50 shares, FIFO means those 50 shares come from your original 2020 purchase.

FIFO is the IRS default method. This means if you don’t explicitly tell your broker which method to use when you sell, you’ll automatically be treated as if you chose FIFO. That’s important to understand because it happens without any action on your part.

Why LIFO Can Save You Money on Taxes (But Has a Catch)

LIFO, or last in first out, works in the opposite direction. With LIFO, you sell the shares you bought most recently. Using the same example, you’d be selling your 2025 shares first, leaving your 2020 holdings untouched.

The appeal of LIFO is straightforward: newer shares typically have a smaller profit built in. Since stock prices generally rise over time, your most recent purchases are often cheaper than your oldest ones. By selling those recent purchases first, you minimize your taxable gain in any given transaction.

However, there’s a trade-off. LIFO requires you to actively elect this method with your broker—it won’t happen automatically. More importantly, because you’re selling shares you’ve held for a shorter time, you’re more likely to face short-term capital gains taxes rather than the more favorable long-term capital gains rates.

FIFO vs. LIFO: The Key Tax Differences

FIFO’s main advantage stems from its time dimension. By selling your oldest shares, you’re typically realizing gains on investments you’ve held for years—often more than a year. That length of ownership matters because long-term capital gains receive preferential tax treatment with lower rates compared to short-term gains.

The downside is that older shares acquired when prices were lower create larger gains. If a stock you bought at $20 is now worth $100, your taxable profit on that share is $80. With FIFO, you’re forced to claim that large gain when you sell.

LIFO lets you choose your shares strategically to minimize gains in any single transaction. But you’re paying for that flexibility. The shorter holding period on recently purchased shares often means you’ll owe short-term capital gains taxes, which are taxed at ordinary income rates—significantly higher than long-term rates.

One Critical Step That Protects Your Tax Strategy

Regardless of which method you choose, there’s one non-negotiable requirement: get written confirmation from your broker documenting your election. This matters more than most investors realize.

If your broker doesn’t send written verification, the IRS can claim you never made an affirmative election. That means they can force you to use FIFO by default, regardless of what you intended. Having documentation on file protects you from this scenario and ensures your carefully planned tax strategy actually holds up if audited.

Making the Right Choice for Your Situation

Your decision between first in first out and LIFO depends on several factors. If you have significant gains on your oldest shares, LIFO’s tax reduction might justify paying the higher short-term capital gains rate. If you’re selling shares that haven’t appreciated much, FIFO’s preferential long-term treatment may serve you better.

The key is being intentional about the choice rather than letting the IRS default determine your outcome. Being tax-smart when selling shares directly impacts how much of your investment gains you actually keep.