An assignment is not permissible for document type &1 (PCO)

What causes this issue?

You cannot assign the document type &v1& to a request category because
this document type is defined as a document type for input tax
adjustment postings in the global settings for public-owned commercial
operations. This document type can only be used for postings.

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?

Select another document type.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.