Hi, I believe currently IFS does not have standard option to validate the PO status when creating the Supplier invoice. Therefore users are able to create manual supplier invoices for even cancelled orders or already paid orders. However, since user is required to match PO receipts for counter postings, user will not be able to proceed further with the Invoice as there are no receipts to match against. 

You can use a custom event to trigger upon saving the supplier invoice to validate the PO status. But it will be a error message and not a warning message.

Hope this will help.

Thanks and Regards,

Akila

Same issue has been previously reported to RnD and below is RnD explanation on that.

Issue:

Cancelled PO part line can be invoiced in Manual Supplier Invoice. This behavior is misleading. 

RnD Explanation (Solution ID: 263748):

“The Show All button will only display purchase order receipts that have either been invoiced or are pending invoicing. It will not show part/ no part lines that have been cancelled or are pending receipt. In the reported issue it is possible to identify which line of the purchase order is being displayed in the Match PO Receipts dialog by referring to the columns Receipt No, Line No and Release No (when the show all button is selected).

The Receipt Qty/Price Qty to Match is zero in this situation as the quantity on Line 1 of the purchase order has been invoiced in total. Once the user attempts to match the same purchase order line for the second time the Status Detail Info will display the following information "No matching has been conducted. Either line matching is selected and information is missing on the invoice lines compared to the Purchase Order Reference or a Sub Contract Reference is added and the invoice must be manually matched." which indicates the line cannot be matched again in full except for an instance where the user decides to add an additional cost.

Hence the reported issue is not considered a bug in the system.”