Transaction refused as a result of a duplicate invoice ID supplied.

[bmoore]

We've created a product/service that charges $2,000 one-time, for consulting work. We need to add this product/service to a client who bought the same product/service last month. When we do this, the charge is unsuccessful and the Gateway Log shows the following:

 

Duplicate trans: XXXXX-The transaction was refused as a result of a duplicate invoice ID supplied. Attempt with a new invoice ID.

 

The invoice created by WHMCS is a new invoice ID. Original invoice that charged $2,000 successfully was 124. Newest one was 145. When we changed the following PayPal setting from Yes to No, we were able to charge the customer. But our PayPal rep has told us NOT to leave this setting set to No:

 

Block Accidental Payments:

You may prevent accidental payments by blocking duplicate Invoice IDs

 

X Yes, block multiple payments per invoice ID

No, allow multiple payments per invoice ID

 

Is there any setting in WHMCS that we can adjust that will allow us to add the same product/service to the same customer in a subsequent month and have the charge go through successfully? Thanks much.