Thank you for your question.
If by alter you mean change the RRSP deduction limit, then no. You cannot claim a larger RRSP/PRPP deduction than your contribution room allows you to. If you do, you will have to pay a tax on the excess amount.
However, you can contribute to your RRSP during 2020 and the first 60 days of 2021.
To update your RRSP deduction, follow these instructions:
1) Log into your TurboTax account.
2) Click on "Find" on the top right of your screen and type in RRSP profile
3) Confirm you made RRSP contributions during the allowed time frame.
4) Click yes on "Do you want to change this amount?" on the next page
5) Update RRSP deduction limit
If you have any questions, you can contact our phone support team or contact us via private chat on Facebook or Twitter.