Here’s an overview of how cryptocurrency taxes work.
Specifically, what you’ll do is net all your short term capital gains/losses across all asset classes (e.g. crypto, stocks, etc.) and same for long term capital gains/losses across all asset classes. Then you will sum net short term capital gain/loss (across assets) and net long term capital gain/loss (across assets). If the total amount is still negative (loss), you can offset a portion of ordinary income (~$3K) and roll over the rest of the net loss to future tax years. You can do this for each tax year, and roll forward losses (but not backward, and not gains).
Say for example I have a 20k gain in 2017 and a 40k gain in 2018 would I then have a tax write off of 147k?
In this example, you would capital gains tax on $20K of capital gains in 2017, on $40K of capital gains in 2018, and in 2019 you would offset your income by a few thousand and roll over the remaining $140K+ loss to 2020. Then in 2020, any gains could be offset by this net amount rolled over.
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