The most common types of Indefinite Delivery, Indefinite Quantity (IDIQ) contracts are definite-quantity, indefinite-quantity, and requirements contracts, as described in FAR Part 16.5. These contract types all allow for the ordering of supplies or services during a specified period, but they differ in how the quantities are determined and committed.
A definite-quantity contract provides for a definite quantity of specific supplies or services for a fixed period, with deliveries or performance to be scheduled at designated locations upon order. An indefinite-quantity contract provides for an indefinite quantity, within stated limits, of supplies or services to be furnished during a fixed period. The government places orders for individual requirements. A requirements contract provides for filling all actual purchase requirements of designated Government activities for supplies or services during a specified contract period, with deliveries or performance to be scheduled by placing orders. The GSA Multiple Award Schedule (MAS) contract is a prominent example of an IDIQ, which can have a term of five years with three five-year options, totaling up to 20 years. State and local government entities also use similar vehicles, which are governed by their specific state procurement codes and portal vendor guides.