The intent is to see the complete life cycle of a purchase order
  1. We send a PO to a supplier
  2. We receive the goods
  3. We receive an invoice for the goods
  4. A bill is then created, this Bill is directly linked to the respective PO in the Bill we can then attached the supplier invoice, it will have the supplier invoice number, ability to update and alter any pricing or delivery charges.
This will allow us to easily track down supplier invoices related to a job.