https://www.questrade.com/learning/goal-tracking/retiring-comfortably/if-you-have-a-pension-plan-do-you-need-an-rrsp#:~:text=If%20you%20have%20a%20company,a%20work-based%20pension%20plan.
Check your contribution room—you may have more than you think
If you have a company pension plan, an amount called the Pension Adjustment (PA) is deducted from your RRSP contribution limit. The PA is the estimated value of the pension benefits an individual has earned during the year and is deducted for anyone who is on a work-based pension plan. The PA was established by the Canada Revenue Agency to level the playing field for pensioned and non-pensioned Canadians alike, so the higher the value of your pension the higher your PA amount will be.
If you are in a defined contribution plan, where you contribute a fixed percentage of your total income to your pension—which may be matched by your employer—your PA will be the amount you contributed plus the matched amount. For a defined benefit pension plan, your PA is calculated as: [(9 X your annual accrued benefit) – 600]