Contract modifications are of the following types:

      (a) Bilateral. A bilateral modification (supplemental agreement) is a contract modification that is signed by the contractor and the contracting officer. Bilateral modifications are used to-

           (1) Make negotiated equitable adjustments resulting from the issuance of a change order;

           (2) Definitize letter contracts; and

           (3) Reflect other agreements of the parties modifying the terms of contracts.

      (b) Unilateral. A unilateral modification is a contract modification that is signed only by the contracting officer. Unilateral modifications are used, for example, to-

           (1) Make administrative changes;

           (2) Issue change orders;

           (3) Make changes authorized by clauses other than a changes clause (e.g., Property clause, Options clause, or Suspension of Work clause); and

           (4) Issue termination notices.