In order to calculate the share value while selling, you need to compare value of the share sold, brokerage commission, transaction fee and sales returns. It sounds easy but in reality we have to deal with stuff like DIRP (Dividend Reinvestment Program). One important thing that you should not forget is the share purchase by means of Dividend Reinvestment Program.
In case, you have misplaced all your important statement of transaction, and there is no scope of recovery, you can check with your broker, whether he can grant you the information or not. If in case, you cannot get the information from the broker, you can go to the micro film room in any local library. In this micro film room, you can find the high and low price of the acquisition date, and then calculate. The result will be approximately what you are seeking. It is not necessary to have the exact information. Even if you try and give your best shot, you will be close to the IRS.
In case, you have misplaced all your important statement of transaction, and there is no scope of recovery, you can check with your broker, whether he can grant you the information or not. If in case, you cannot get the information from the broker, you can go to the micro film room in any local library. In this micro film room, you can find the high and low price of the acquisition date, and then calculate. The result will be approximately what you are seeking. It is not necessary to have the exact information. Even if you try and give your best shot, you will be close to the IRS.