FIFO
TAXDEFINITION
First-in, first-out — the default lot-accounting method that assumes the bitcoin you sell is the oldest bitcoin you bought, used to calculate cost basis across multiple lots.
If you bought bitcoin in 2022, 2024, and this year, and then sell some, the tax code needs a rule for which lot you sold. Absent any other election, the IRS defaults to FIFO — you're assumed to have sold your oldest coins first, using their cost basis to calculate the gain.
The alternative is specific identification: naming the exact lot you're selling, provided you kept contemporaneous records identifying it. Specific ID can lower a tax bill by letting you sell a high-basis lot instead of an old, cheap one — but it only works if your records can prove which lot you meant before you filed.
IN A SENTENCE
“Under FIFO, his sale used up the 2022 lot first — the one with the lowest cost basis and the biggest gain.”
Key facts
Common questions
Can I switch from FIFO after the fact?
No — specific identification has to be made at the time of the sale, not reconstructed later once you see which method owes less tax.
Does every exchange track lots for me?
Some do, inconsistently. Don't assume — export your own buy history yearly so you can verify or override what an exchange reports on your 1099-DA.