The total amount you can contribute to your RRSP each year is made up of your contribution limit for the current year plus any "carry-forward" contribution room from previous years.
Your RRSP contribution limit for 2021 is 18% of earned income you reported on your tax return in the previous year, up to a maximum of $27,830. For 2020, the dollar limit was $27,230. If you have a company pension plan, your RRSP contribution limit is reduced – see the last bullet point below for details.
If you don't make the maximum allowable RRSP contribution in any given year, Canada Revenue Agency (CRA) lets you carry forward the unused contribution room indefinitely and add this to the amount you can contribute for future years.
Both your annual contribution limit and any carry-forward contribution room are shown on your notice of assessment.