There is no impact on capital gain treatment upon the sale of shares that have been lent through the Stock Yield Enhancement Program.
The lender of the securities is entitled to receive the amount of all dividends and distributions made on loaned securities through the Stock Yield Enhancement Program.
The cash payment is the same amount but depending on your tax status, may be treated differently. IBKR takes steps to prevent SYEP lenders from receiving a payment-in-lieu of a dividend (“PIL”). However, there may be cases where the account receives PIL.