CPP from annual payroll after opt out

I have a client who opted out of CPP on her 65th b’day in July 2020. She is an active shareholder in a Corporation. We paid her an annual salary on December 31, 2020. No CPP was deducted. Should we have averaged her earnings & calculated CPP?

If she properly opted out, there is no CPP calculation for a payment on December 31, 2020.

The form, CPT30, “Election to Stop Contributing to the Canada Pension Plan, or Revocation. . .” is completed and filed with Canada Revenue Agency. If this was done in July, 2020, great!