How does sending Bitcoin affect my tax lots?

When you send Bitcoin from River, the amount you send is deducted from your account using the FIFO method starting with all Unknown Tax Lots then Known Tax Lots. First In, First Out, commonly known as FIFO, is an asset-management and valuation method in which assets received or bought first are sent and sold first.

This method will deduct from the oldest Tax Lot in your River account. If the Bitcoin Send is smaller than the Tax Lot selected then that amount will be removed and the rest will remain. The Cost Basis Per Unit will remain the same for however much Bitcoin remains in the Tax Lot. If the Bitcoin Send is bigger than the first Tax Lot selected then the remainder will be deducted from the next oldest Tax Lot based on the FIFO method.