A computer-implemented method and apparatus for determining a cost basis associated with a plurality of shares of a security. In response to information identifying an issuer, the purchase date and the sale date, a list of capital events that occurred in connection with the security between the purchase date and the sale date is retrieved from a database. One or more shares held adjustment ratios are then retrieved from a database. Each of the shares held adjustment ratios corresponds to one of the capital events that occurred in connection with the security between the purchase date and the sale date. A current cost basis associated with the security may then be determined in accordance with the one or more cost adjustment ratios and the purchase price per share of the security.