HIFO tax rule

[Unsaint32]

For cryptocurrency tax, I use HIFO as the cost basis accounting method. I know I should've gone with FIFO for simplicity.

I'm not 100% clear on the definition of "cost basis" according to the US IRS cryptocurrency rules. Is it the cost of 1 unit (1 BTC) at the time of purchase, regardless how much I purchased? Or, is it the cost of the total purchase?

Let's say here is what I have in my wallet.
Lot A: 0.2 BTC I bought for $6,000 when 1 BTC was $30,000.
Lot B: 0.5 BTC I bought for $10,000 when 1 BTC was $20,000.

Per crypto HIFO rule, if I spend 0.1 BTC from the wallet, am I spending from the lot A or lot B?

[hero_the_bossman]

Did you try to ask Chat GPT or any other LLM for that matter beforehand?