SAP to ARIBA interface error for Payment Proposal Request

[former_member569600]

Hi We have an interface to SAP to Ariba for payment proposal request.

although we are getting message failed for one vendor all the time saying "Bad Request". these are the process steps ;

1) Open invoices from the vendor send to vendor to give us a discount for an early payment ; however for this vendor always only a cleared invoice (paid invoice ) is also sent through message , therefore we are getting the failed message.

when we check the particular invoice we find this Invoice is already paid before the cXmal message sent from SAP to Ariba.

Then why the first place this invoice got selected for payment proposal request? attached the error screen shot here with