Payroll deductions are money you hold in trust for the CRA — so the remittance deadline matters as much as payday itself.
Regular remitters: your payroll deductions (CPP, EI and income tax withheld) are due by the 15th of the next month. Smaller and newer employers may remit quarterly, while larger payrolls remit on accelerated schedules — your remitter type is set by the CRA based on your average monthly withholding.
Miss the date and penalties apply from the first day late, growing the longer the remittance is outstanding, with interest charged on top. The fix is boring and perfect: calendar the due date the moment payroll runs, every time.