Source Deduction Remittance Vouchers and payments must be received by CRA on or before the due date.
Source deductions are reported on a weekly, monthly, semi-monthly, or quarterly basis.
Your reporting period is subject to change if it meets certain criteria.
Monthly remittances (the most common reporting period for small businesses) must be received by CRA on or before the 15th day of the month following the reporting period.
Quarterly remittances must be received on or before Jan 15, Apr 15, July 15, and Oct 15.