If you bought the same coin in batches and now want to sell only a portion, the platform won't automatically select the most cost‑effective batch—it follows a default rule. Different rules calculate your gains and tax completely differently.
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Choosing between FIFO, LIFO, and HIFO isn't just accounting—it directly decides how much tax you owe this year. The right option depends on your position structure, your tax goal when selling, and whether you keep detailed trading records.
Step 1: Find Out Which Method You Can Use Right Now
Different platforms have different defaults, and not every method is legal everywhere.
Case A: The platform default and most common – FIFO (First‑In, First‑Out) Major exchanges like Binance and OKX default to FIFO, meaning the earliest coins you bought are sold first. Tax effect: In a bull market your early buys often have a low cost. FIFO will show higher gains, so you pay more tax; but if you held them over a year, a lower long‑term capital gains rate may apply. How to know you're using it: If you've never changed the cost basis setting, you're already on FIFO.
Case B: Want to pay less tax in a bull market – LIFO (Last‑In, First‑Out) The most recently bought coins are sold first. OKX and some US platforms support this method, but some regions (such as Australia) do not accept LIFO. Tax effect: In a bull market, recent buys usually have a higher cost. Selling them first lowers your gain and reduces your immediate tax bill. Risk warning: In a bear market LIFO can inflate your gains and cost you more tax. Also, if the recent coins are held under a year, even a smaller gain is taxed at high short‑term rates, which can offset the savings.
Case C: Want to maximize tax savings – HIFO (Highest‑In, First‑Out) Regardless of purchase date, the most expensive coins are sold first. The US IRS allows this method, but only if you can identify exactly which lot each sale comes from. Tax effect: It pushes your taxable gain as low as possible, usually the most tax‑efficient choice for long‑term traders. What you need: A detailed record of every purchase—date, cost per coin, quantity (often called a "lot record"). Without one, HIFO won't be accepted and the IRS will treat your sales as FIFO.
Step 2: Run All Three Methods on One Holding to See the Gap
Take an actual position and test how different the gains come out.
How to do it: Suppose you hold a coin bought in three batches:
| Lot | Quantity | Cost per coin | Holding period |
|---|---|---|---|
| A | 100 coins | 10 U | Over 1 year |
| B | 50 coins | 20 U | Over 1 year |
| C | 75 coins | 15 U | Under 1 year |
Now you sell 120 coins at a price of 30 U each.
FIFO: Sell A first (100 coins), then B (20 coins). Gain = (30-10)×100 + (30-20)×20 = 2,000 + 200 = 2,200 U. Both A and B are long‑term, taxed at a lower rate (e.g., 15%).
LIFO: Sell C first (75 coins), then B (45 coins). Gain = (30-15)×75 + (30-20)×45 = 1,125 + 450 = 1,575 U. C is short‑term (taxed up to 37%), B is long‑term (15%).
HIFO: Sell B first (50 coins, highest cost), then C (70 coins). Gain = (30-20)×50 + (30-15)×70 = 500 + 1,050 = 1,550 U. Mix of long‑term (B) and short‑term (C) rates.
What this shows: On the same sale, FIFO gives the highest gain and HIFO the lowest. Converted to tax, the difference could be thousands of U.
Step 3: Pick a Method Based on Your Situation and Lock It In Before You Sell
Once you choose a method, you can't switch it per sale—the IRS requires you to decide the identification rule before the sale, not when filing taxes.
Case A: You trade often and want simplicity. Pick FIFO. It's the platform default, needs no extra records, and long‑term holdings get favorable rates. The downside is more tax in a bull market.
Case B: You trade often, want to optimize taxes, and keep full records. Pick HIFO. It minimizes your current taxable income. But you must have a complete lot record for every purchase: date, cost per coin, quantity, transaction hash or platform order ID.
Case C: You mostly take short‑term swings and recent buys are at high prices. Pick LIFO. It quickly lowers paper gains. Note that LIFO isn't legal everywhere and can backfire in a bear market.
Risk warning: If you choose HIFO or LIFO but your platform only supports FIFO, you cannot simply "correct" it to HIFO on your tax return—unless you have independent lot‑level records and clearly earmarked which lot was sold at the time of the trade. Otherwise the IRS defaults to the platform's FIFO report, and your HIFO numbers will be rejected.
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How to Verify After You Pick a Method
Once you've chosen, manually calculate your realized gain using your lot records and compare it with the platform's figure:
If the platform uses FIFO and you use HIFO, the two gain figures will differ—that's normal. The key is that your tax software (like Cointracking or Koinly) matches your chosen method, not necessarily the platform.
If your platform supports your method (e.g., OKX supports LIFO), check the "cost basis" setting to confirm your preference is saved, so every future sale follows the same rule.
What to do next: Spend 10 minutes to make a list of all your current buys—time, quantity, cost per coin—and save it locally. Whether you end up with FIFO, LIFO, or HIFO, this list is your foundation. Each time you buy a coin later, add that batch. At tax time, run your chosen method directly from this list; it's faster and more under your control than waiting for exchange reports.
