It is not feasible to apply/add the "Charge Code" during the PO Product Receipt in out of box feature, only the "view charges" button is available.

But it is a justified requirement for those clients; who are managing the PO process through the few separate departments / teams such as "PO creation, PO product receipt and PO invoicing" department / team; controlling by the Roles and security.

For this kind of scenario the product receipt team unable to add the charges; since the PO product receipt team won't have access to modify the PO lines.