As per the Canada Revenue Agency (CRA):
Do not report any amount using box 16A if your employee has not reached the first maximum earnings ceiling, use box 16.
Do not report any amount using box 16A if your employee does not have already have their maximum CPP contribution reported in box 16.
So you can either ask for an amended T4 from your employer, or as per our FAQ: If you have at T4 where Box 16A has an amount, Box 16 is empty, and box 26 is empty (no “0”) or has an amount, then remove the amount that’s in box 16A and enter that amount in box 16 instead.
