You would get taxed twice, but it wouldn't stack. If you earned $15 of Bitcoin, you'd get $15 added onto your tax bill at payout. Then if Bitcoin jumped to $20

You would get taxed twice, but it wouldn't stack. If you earned $15 of Bitcoin, you'd get $15 added onto your tax bill at payout. Then if Bitcoin jumped to $20 and you sold it a couple months later, you'd have the $5 difference of short-term capital gains taxes added on then.