Ref.: - Message - VAT Business Posting Group is not allowed for Branch
When trying to receive, ship or post a document where non-system generated comments have been added manually, a VAT error is possible (which could be due to one of several other possibilities), but in this case, the 'Type' in the document Lines section.
Issue
Trying to receive a purchase order but the system offers a VAT Business Posting Group error message.
For e.g.

Resolution
Open the document which is being received (ctrl+f5) & look for a manually added comment(s) line. Check the 'Type' column & ensure it is blank.

If the column is not present, add it using 'Show Column'.
Right click on any field caption & choose Show Column, select 'Type'.
Example

Template v0.03, MPE, 08/11/2022