48 CFR 43.104: 43.104 Notification of contract changes.

(a) When a contractor considers that the Government has effected or may effect a change in the contract that has not been identified as such in writing and signed by the contracting officer, it is necessary that the contractor notify the Government in writing as soon as possible. This will permit the Government to evaluate the alleged change and (1) confirm that it is a change, direct the mode of further performance, and plan for its funding; (2) countermand the alleged change; or (3) notify the contractor that no change is considered to have occurred.

(b) The clause at 52.243-7, Notification of Changes, which is prescribed in 43.107, (1) incorporates the policy expressed in paragraph (a) above; (2) requires the contractor to notify the Government promptly of any Government conduct that the contractor considers a change to the contract, and (3) specifies the responsibilities of the contractor and the Government with respect to such notifications.