Basic rate &1 and conditional rate &2 have different RTP categories

What causes this issue?

Basic rate &V1& and conditional rate &V2& (rate relationship group &V3&)
are used in a substitute rate relationship. In this case, the rates must
have an identical <DS:DE.RTPCATEGORY>RTP billing categories</>.
However, the basic rate and the conditional rate have different RTP
categories.

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?

For substitute rate relationships, only use basic rates and conditional
rates with identical RTP categories.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.