Discount was entered even though no discount relevant line items exist

What causes this issue?

Although none of the line items is liable to cash discount in G/L
account or assets accounting, a cash discount was entered in the
customer or vendor area of a line item.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Please correct the document either by deleting the cash discount or by
indicating line items as liable to cash discount in G/L account or
assets accounting.

Error message extract from SAP system. Copyright SAP SE.