You must have a service plan with EFT to process pre-authorized payments. 

1. In the customer record, go to the Pre-Authorized Debit tab.
2. Select This customer has a signed active preauthorized-debit agreement checkbox.
3. Fill in the customer's banking information and click Save and Close.
   
4. When creating a sales invoice, select Pre-Authorized Debit (PAD) from the Payment Method dropdown.
5. Process the invoice as required.
6. Set up the EFT.
7. Generate the .DAT file and submit it to your bank.