Where do I enter additional payments into a pension plan that don't show on my T4?

[TurboTaxSusan]

If you made past service contributions in 2024 to a pension plan for which you have a receipt and which are not included on a T4 or T4A slip, click on "2024 tax return" in the top left. Then search for "Registered Pension Plan Deduction (RPP)".