I traded crypto in 2018 2019 2020and 2021 I have 2 missing cost basis transactions for my capital gains reportone is for the year of 2019 and one is for the year of 2021

[osnapitzmylz]

My capital gains are much higher than I expected , like exponentially higher, and the missing cost basis is saying a nice size of BTC I acquired is missing and unaccounted for but all my trading data has been imported, would the 2019 missing cost basis transaction effect my returns for 2020 tax return?

[fanfare]

you must know the number of bitcoin you sold and the proceeds for those.

That must all  be reported to IRS.

If you do not report the correct basis, but use zero basis you are overpaying on your capital gains tax.