Say I want to buy something, like a truck for example, with my #Bitcoin that I legally bought with my post-tax labor wages.

10% in local sales taxes and title fees

+

15% federal capital gains tax on an *indeterminable appreciation*

Forget the ridiculous 25% tax amount for a moment. How do I determine my #Bitcoin cost basis on several years of small DCA purchases? Is the expectation to guess and consequently lie on a tax return? Bc the actual cost basis can't be accurately proven, and would require enormous effort to attempt.