In circumstances when you don't have time to get bids, it pays to have forged strong relationships with vendors you can trust. The purchase order you send to the supplier is, in fact, a legal offer to buy. Once accepted by the supplier, it constitutes an enforceable contract. Therefore, it is important to complete purchase orders with care. There may be times when you want to use a more formal contract, for example, if you are relying on a company for large orders that constitute the bulk of your materials.
Some companies use contracts for all supplier-related purchases.
Any contract you use should be drafted or at least reviewed by an attorney. The contract might address specifics relating to materials, time of performance, payment, termination, liens and claims, and default. If your supplier doesn't perform, you can refuse to pay, and of course you can refuse to do further business with that company. The relationships you have with reliable vendors are precious and should be nurtured. Make a point of meeting with your key suppliers on a regular basis.