Defining Authorizations for Document Types 
Use
You can define a special authorization for every document type. To do this, you need to determine what document types in which form employees are allowed to process.
Authorizations are checked for the following activities:
The system does not check the authorization for document types that are not assigned an authorization group.
Procedure
Maintain Authorizations under Financial Accounting Global Settings.
For each document type, you can specify whether users are required to enter a reference number or the document header text.