1. This is the gross base cost of all shares you bought through the institution. You must NOT use this value on your return.
To calculate the base cost of the shares that you sold, you will have to deduct the profit / loss from the proceeds and then enter this amount in the base cost field on your return.
2. This is the proceeds i.e the value that your shares were sold for. This amount needs to be entered as proceeds in the capital gains section of your tax return.
3.This is the net capital gain / loss. It is the difference between the base cost and the proceeds. You don't have to enter it in your return as it is automatically calculated.