Wouldn't that would work against you unless you cash out your gains slowly to avoid being flagged? I mean, if you have no proof of the OTC transaction, then on

Wouldn't that would work against you unless you cash out your gains slowly to avoid being flagged? I mean, if you have no proof of the OTC transaction, then on whichever amount the government tried to contest they may try to tax you on the full value of the coins at time of sale versus only taxing you on the (presumably positive) price delta.