As per this CRA guide for employers: https://www.canada.ca/en/revenue-agency/services/forms-publications/publications/rc4120/employers-gu...
Box 20 – RPP contributions: Report the total amount the employee contributed to a registered pension plan (RPP). Include instalment interest (for example, interest charged to buy back service).
If your RRSP contributions are not on your T4 slip, then you should have gotten a Group RRSP Contribution receipt.
