How Does FIFO Accounting Work for Selling Cryptocurrency?
Someone who buys crypto in small batches over months or years ends up holding units purchased at different prices, and when it’s time to sell, the accounting method chosen to identify which units were sold can meaningfully change the reported gain.
The short answer
FIFO stands for first-in, first-out, and it’s an accounting method that assumes the earliest units acquired are the first ones sold. When prices have generally risen over time, FIFO tends to match a sale against the oldest, typically cheapest, cost basis available, which can produce a larger taxable gain than a method that instead matched the sale against a more recently acquired, higher-cost unit.
A simple hypothetical
Imagine someone bought crypto three separate times: an early purchase at a lower price, a middle purchase at a moderate price, and a recent purchase at a higher price. If they later sell a portion equal to roughly the size of that first purchase, FIFO assumes those oldest, cheapest units are the ones being sold. The gain is calculated as the sale price minus that oldest cost basis — and because the oldest units were the cheapest, the resulting gain is often the largest possible outcome among the batches available, compared to matching the sale against one of the pricier, more recent purchases instead.
Why FIFO tends to produce a larger gain in a rising market
Cost basis is simply what was originally paid for a given unit, adjusted for certain fees. In a period where prices have generally climbed, the earliest purchases usually carry the lowest cost basis. Because FIFO always draws from the oldest available lot first, it systematically pairs sales with the cheapest available basis during a sustained uptrend, which mechanically produces a bigger spread between sale price and cost basis — and therefore a larger reported gain — than pulling from a more recently acquired, higher-cost lot would.
How FIFO compares to other approaches
- FIFO (first-in, first-out). Always treats the oldest lot as sold first, regardless of which lot would produce the most favorable tax outcome.
- HIFO (highest-in, first-out). Instead identifies the highest-cost lot as the one sold, which is covered in more detail when looking at how HIFO accounting can reduce taxable crypto gains.
- Specific identification. Lets the holder identify exactly which lot is being sold, provided sufficiently detailed records support the identification, offering the most flexibility of the three.
Not every method is available in every situation, and the rules governing which method can be used, and whether it can be changed later, are among the areas where switching from FIFO to specific identification mid-year raises its own set of questions.
Why this matters beyond the math
The accounting method chosen doesn’t change how much crypto was actually sold or for how much — it changes which specific cost basis gets matched against that sale, which in turn changes the size of the reported gain or loss. That makes the underlying challenge of tracking cost basis across every purchase, on every platform, foundational to using any method accurately, FIFO included. Without a complete transaction history, it’s not possible to apply FIFO, or any other method, with confidence.
What to weigh
FIFO is often the default method used when no other identification method has been properly documented, which makes it worth understanding even for someone who doesn’t plan to use it deliberately. Because it draws from the oldest, often cheapest, purchases first, it can produce a larger taxable gain during a sustained price increase compared to alternatives. The rules around which methods are permitted, and how they must be documented, are set externally and can change, so this is an area where careful records and, where the stakes are meaningful, professional guidance tend to matter more than memorizing any single method’s mechanics.