To begin with, Purchase Orders (POs) are contracts by themselves.
- POs are used in simple transactions of goods, such as those under alternative methods of procurement. In contracts awarded thru public bidding, there is a Contract Agreement Form that should be used.
- Since POs are contracts, the Civil Code of the Philippines apply suppletorily to your question. Contracts are perfected by mere consent. If the offer is definite and the acceptance is absolute, and the object and considerations are present, there is a contract already. The written PO is just to formalize what has been contracted.
Note: The PO form came from the COA.