That's how I do it with mutual fund shares, which would be a similar situation to Bitcoins due to it all technically being one "pot". If you use a tax-lot spec

That's how I do it with mutual fund shares, which would be a similar situation to Bitcoins due to it all technically being one "pot". If you use a tax-lot specific accounting method FIFO/LIFO/highest cost/other specific, you just need to track which "lots" you've already sold out of (fully or partially), and ensure that you don't sell something twice. Now, if you used average cost at some point, you're kinda screwed if you want to switch to specific lot.