The payment reference for payments in is ‘SODBG-accountid’.
The first part of the reference is always SODBG.
The Account ID is the 7-digit combination of numbers and letters found on the client’s account record, e.g., 01A23B4. In this example, the payment reference could be SODBG-01A23B4.
We have a template Payment Instruction document that you can present to your client which can be found here.
See also What bank details should my client send contributions to?