The sales proceeds figure, as defined in your tax forms, is simply the amount of money you received in exchange for selling your shares this year. The cost basis is the amount of money you paid to purchase the shares that are being sold, with possible adjustments for wash sales and non-dividend distributions. Your sales proceeds and cost basis on your 1099-B may be much higher than your portfolio’s earnings or balance was at any given time, because these proceeds represent the total amount of ...