We consider you to have made your tax payment on the day that:
If you mail your payment, we consider you to have made the payment on the day we receive the payment, not on the day you mail it [subsection 248(7) of the Income Tax Act].
If your payment due date falls on a Saturday, a Sunday, or a public holiday, the payment will be considered received on time if it is received on the first business day after the due date.