Prepayment is not possible in combination with retention

What causes this issue?

You want to settle the invoice through prepayment. One or more of the
invoice items contain a retention.

System Response

The system cannot save the invoice with the creation of a prepayment
document.

How to fix this error?

Delete either the prepayment status in the invoice header or all
retention amounts at item level. You can then save the document.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.