@kleje007
No the closing price of GBTC doesn't come into play for any transactions that were not sales of your holdings, just the reported "proceeds" ones. I just posted an equation to calculate cost.
To explain what is going on here, is holders of the trust have to pay taxes on whatever the trust does inside. To pay expenses they sell some Bitcoin off, which will generate a capital gain or loss depending on when you acquired GBTC.
