Change orders are also unilateral changes that direct contractors to make a change authorized under the "changes" clause of a contract. Most contracts have a changes clause, either FAR 52.232-1 for fixed price contracts or FAR 52.232-2 for cost type contracts or FAR 52.232-3 for time and material contracts. Change orders usually result in an equitable adjustment.
Other examples of unilateral changes include
- make changes authorized by clauses other than a changes clause (e.g. property clause, options clause, or suspension of work clause)
- termination notices
Bilateral modifications (aka supplemental agreements) is a contract modification that is signed by both the Government and contractor. Bilateral modifications are used to
- make negotiated equitable adjustments resulting from the issuance of a change order
- definitize letter contracts and
- reflect other agreements of the parties modifying the terms of the contract
See FAR Part 43, Contract Modifications, for regulatory coverage of contract modifications.