Document has been prepaid, do not enter retention

What causes this issue?

A down payment document has been posted for this invoice document. You
cannot enter retention for prepaid invoices.

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

INCLUDE MM_IV_MELDUNGEN OBJECT DOKU ID TX

System Response

How to fix this error?

Delete the retention values at item level.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.