Combination DPC with down payment and/or retention not allowed

What causes this issue?

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

System Response

It is not possible to save a purchase order item linked to a down
payment chain (DPC) contract with down payment and/or retention values
in the purchasing area.

How to fix this error?

The purchase order document category used allows you to create a down
payment chain contract for service items. The <LS>DP Chain</> tab at
item level is created correctly.
In this case, make the following settings:
On the <LS>Payment Processing</> tab page at header level of the
purchase order, choose:
Retention # Not applicable
DP Category # No Down Payment
On the <LS>Invoice</> tab page at item level of the purchase order,
choose:
DP Category # No Down Payment
Use either a down payment chain or a down payment and/or retention
values in a purchase order document.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.