How to process supplier credit invoices for Purchase Orders using Payment Milestones?

Hello community,

We are currently facing a functional issue regarding the processing of supplier credit invoices for Purchase Orders managed with payment milestones.

Our customer has paid several supplier invoices linked to a Purchase Order that includes payment milestones. The supplier invoices linked to the PO lines have been fully processed, matched, and paid.
Later, the supplier issued two partial credit invoices related to those invoices.

Under normal circumstances (standard receipt flow), credit invoices are processed using the usual matching/correction process. However, in this case, that approach does not work.

We have already tried:

• the standard credit invoice process which is unsuccessful;
• creating a negative PO line, rejected by the system because negative values are not allowed;
• using Price Adjustment Purchase , no data (no PO line is available for adjustment).

From our investigation, this seems to be standard IFS behavior:

• Payment milestone invoices are amount-based only, not quantity-based, so invoice matching is performed only against milestone amounts.
• Because of this, fields such as Invoiced Quantity and Invoiced Price on the PO line are never updated.
• As a result, Price Adjustment Purchase cannot be used, since it relies on quantity/receipt logic.

We also found that this appears to be a known product limitation rather than a data issue, and similar cases indicate that standard credit note processing is blocked in milestone-based flows.

Could you please advise:

1. What is the recommended way to process supplier credit invoices when the original invoices are linked to payment milestones?
2. Should the existing milestones be adjusted, or should a dedicated credit milestone be created?
3. Has anyone implemented a workaround for this scenario?
4. Is there any IFS best practice for handling this type of case?

From our research, the only alternatives seem to be:

• a custom workaround (adding a credit line/milestone),
• or a manual accounting adjustment outside the standard PO/AP flow.

Thanks in advance.

Best,

Fatimetou Taleb