We can’t provide advise but try to provide general information to help you take the next step. To calculate your capital gain (or loss), you will need to determine your Adjusted Cost Base (ACB). To determine an accurate ACB you will need to know the cost of the securities purchased (the amount you paid for the security plus any additional costs, such as fees and commissions) and the price at which they were disposed (what the security was sold for). The CRA has outlined rules on how to calculate the ACB, especially if you acquired units of stocks or mutual funds at different points in time. Generally, you have to average the purchase price of the investment you bought during the year and use this average as your ACB. Learn more about how to calculate the ACB of identical properties from the CRA.
We would suggest that you contact your broker or transfer agent to see if they can provide transaction records. If you can’t recover your records you may wish to seek professional tax advice to determine the appropriate options that are available given your financial situation.