If you were fortunate enough to purchase one BTC for $1 and stored it in a cold wallet and then purchased a 2nd bitcoin on an exchange like Coinbase for $100,000 and then sold it hours later for $100,001 according to the US government your taxable gain isn’t $1 it’s $100,000. Using BTC to purchase something without converting it back to fiat doesn’t exempt you from capital gains taxes. Therefore until legislation changes or the government completely fails it’s a mistake to use bitcoin as a means of exchange over fiat unless of course you like to add a self imposed tax on yourself.
Discussion
Wait, huh? That can’t be right. Coinbase would have no way to know about your cold wallet Bitcoin, and would produce a tax document for you showing the $1 short term gain on their platform.
FIFO
Fortunately, since bitcoin isn't fungible, if the coins were kept as separate utxos you can prove you sold the 2nd Bitcoin.
The IRS probably assumes first in first out, curious if anyone has put this to the test.
And you're just wrong about Lightning Network.