Regardless capital gain or loss, you have to file an income tax and benefit return to report the transaction (even if you do not have to pay tax). If you have a capital loss in 2017, you can use it to reduce any capital gains you had in the year, to a balance of zero. If your capital losses are more than your capital gains, you may have a net capital loss for the year. If you have a capital gain, you may be able to either defer part of the capital gain by claiming a reserve, or reduce or offset all or part of the gain by claiming capital gains reduction.
Indicate the amount of gain or loss on your CRA Schedule 3. If the total of your gains for the year is more than your losses (positive result on line 197), you will include the amount on line 199 on line 127 of your return. If the total of your losses for the year is more than your gains (negative result on line 197), do not include the amount on line 199 on line 127 of your return. The CRA will keep track of it and your net losses will appear on your Notice of Assessment statement.
Please consult Guide T4037 for more detailed information