As per CRA instructions for missed reporting of RRSP contributions.

"If you deduct an amount for 2018 that you contributed to an RRSP up to March 1st, 2018, which you had not previously deducted, you should have filled out and sent a Schedule 7, RRSP and PRPP Unused Contributions, Transfers, and HBP or LLP Activities, for these contributions, for each particular year. If you did not, you should fill out and send a copy of the appropriate Schedule 7 for each year, along with the appropriate RRSP receipts, to your tax centre, separate from your 2018 income tax and benefit return."