My employer fired me May 7 2026 without cause. They intend to make a final payment to me May 15 and submit my record of employment to CRA. I do NOT accept this arrangement. Should I confirm my non acceptance by email BEFORE May 15?

If your employer has not made the payment and the issuance of your record of employment/payment contingent on signing/returning a release, then you do not need to confirm that you do not accept the arrangement. Some of the requirements the employer has at the time of termination arise from statutory requirements, including outstanding wages and records of employment. Receiving those entitlements would not waive your potential legal entitlement.