Create a supplier — name, tax registration, classification. Add a site with a remit-to address validated against your geographies. Assign the site to two business units with different default terms. Add supplier bank account details. Show the bulk import path for a supplier master migration. Then review the completed supplier.
Supplier bank account changes are the single biggest fraud vector in accounts payable. The control is independent verification by phone, to a known number — never to a number on the change request itself. Configure approval on bank detail changes where the product allows it. This is a two-minute segment and it is the one people quote back to you.
And the tax registration on the supplier drives the behaviour you configured in the tax module. That loop is closed explicitly here rather than left for somebody to notice.