Excerpt from CRA Website
For individuals
The due date for filing an income tax and benefit return and paying any related tax balance due is April 30, 2021.
Filing on time helps to avoid having any of your benefit and credit payments interrupted or stopped.
For self-employed individuals
If you are self-employed or have a spouse or common-law partner who is self-employed, you both have to file a return by June 15, 2021.
To avoid late-filing penalties, pay any amount you owe by April 30, 2021. After this date, the CRA charges interest on what you owe until your balance is paid.
For a deceased person
If you are filing a return for a deceased person, the due date depends on the date of death and if the person owned a business in 2020.
If you are the surviving spouse of a deceased person or common-law partner and you were living with the deceased, the due date for filing your return is the same as the due date for the deceased person’s return. However, if you have a balance owing, you must pay it on or before April 30, 2021.