As per CRA:
If you or your spouse or common-law partner carried on a business in 2020 (other than a business whose expenditures are primarily in connection with a tax shelter), your return for 2020 has to be filed by June 15, 2021.
However, if you have a balance owing for 2020, you have to pay it on or before April 30, 2021. For more information on how to make your payment, see Make a payment.