The Pre-Authorized Debit (PAD) web service offers preparers an electronic method to submit a payment to the CRA on behalf of a taxpayer. Use it instead of printing the T7DR(A) which requires your client go to their bank to make a payment.
The service is available for paying an amount owing on current-year T1 tax returns. It is not to be used to pay any other amount due to CRA, such as a balance due on prior year returns.
You can use PAD to make multiple payments for a taxpayer; however, only one request can be active at a time. You cannot make another request until the payment date of the active request has passed. Any attempt to do otherwise will generate an error message.