Because the government's needs change from time to time, government contracts contain a clause authorizing the contracting officer to unilaterally order changes in the specifications and other contract terms. The changes must be "within the general scope of the contract." The contractor is obliged to perform the contract as unilaterally changed by the contracting officer. A change is within the scope of the contract if it can be regarded as within the contemplation of the parties at the time the contract was entered into. The government cannot use a change order to change the general nature of the contract. The contractor is entitled to an equitable adjustment in price and delivery schedule if changes are ordered.
Information courtesy of the Small Business Administration.