Change orders, options, constructive changes, and requests for equitable adjustment — how the work and the price get changed after award.
Last reviewed on May 12, 2026 by the Government.biz editorial team against FAR Part 43 and the standard Changes clauses.
A modification is any written change to the terms of an existing federal contract. The rules live in FAR Part 43, and almost every modification is documented on Standard Form 30 (SF-30), "Amendment of Solicitation/Modification of Contract." The SF-30 states the modification number, cites the authority for the change, and shows whether it is bilateral or unilateral.
Understanding modifications matters because this is where contract performance most often goes sideways — and where contractors most often leave money on the table. Knowing when you are entitled to more time or money, and how to ask for it correctly, is one of the highest-value skills in contract administration.
Signed by both the contractor and the contracting officer. Required whenever the change needs agreement — adjusting price, definitizing a change order, modifying scope, or settling an REA.
Signed only by the contracting officer, for actions the government may take without your consent under the contract's existing clauses.
Nearly every federal contract contains a Changes clause — the exact version depends on contract type (FAR 52.243-1 for fixed-price supplies, 52.243-2 for cost-reimbursement, 52.243-3 for time-and-materials, 52.243-4 for construction). The clause gives the contracting officer authority to order changes within the general scope of the contract — to drawings, specifications, method of performance, place of delivery, and similar items. In exchange, it entitles the contractor to an equitable adjustment in price and schedule for the impact of the change.
The clause also imposes a notice obligation: a contractor that believes a government direction is a change generally must assert its right to an adjustment within a defined window (commonly 30 days) and before final payment. Missing the notice window is a frequent and avoidable way to lose an otherwise valid entitlement.
The Changes clause only reaches work within the general scope of the contract. A change so large or different that it is essentially new work is a cardinal change — and a cardinal change is outside the clause. Cardinal changes matter for two reasons:
Whether a change is in-scope or cardinal is a fact question turning on the nature, magnitude, and number of changes relative to the original bargain. When a directed change feels like a different contract, raise the scope question in writing before performing.
Sometimes the government changes your work without issuing a change order at all. The law treats this as a constructive change — and it can still entitle you to an equitable adjustment. Classic categories:
An REA is how you ask the contracting officer to adjust the contract price or schedule for a change. It is a negotiation document, not a lawsuit. A persuasive REA contains:
An REA and a claim are different instruments, and the distinction has real consequences:
| REA | Claim (Contract Disputes Act) | |
|---|---|---|
| Nature | Business request to negotiate | Formal demand for a final decision |
| Certification | DFARS cert for DoD over SAT | CDA certification required over $100,000 |
| Interest | Generally none until it becomes a claim | Interest runs from receipt of the certified claim |
| Outcome | Negotiated bilateral modification | Contracting officer's final decision, then appeal to a board or the Court of Federal Claims |
| Cost recovery | REA prep costs can be recoverable as contract administration | Claim prosecution costs are generally not recoverable |
Most contractors pursue an REA first to preserve the relationship and recover preparation costs, then convert to a certified claim only if negotiations fail. See bid protests for the separate pre-award dispute track.
A bilateral modification (supplemental agreement) is signed by both parties and used when the change requires agreement on price or scope. A unilateral modification is signed only by the contracting officer for actions the government can take alone — administrative changes, option exercises, change orders, and funding mods.
An REA is a business request to negotiate an adjustment. A claim is a formal demand under the Contract Disputes Act for a contracting officer's final decision; claims over $100,000 must be certified, and they start interest running. Contractors usually try the REA route first.
Government conduct that changes the work without a formal change order — defective specs, improper rejection, government-caused delay, or directed acceleration. If it adds cost or time, you may be owed an equitable adjustment, but you must give prompt written notice and document the impact.
For an in-scope unilateral change order, yes — perform the changed work and pursue the adjustment afterward. For a suspected cardinal change (work beyond the contract's general scope), raise the scope objection in writing before performing, because that work may be outside the Changes clause entirely.
Authoritative sources: FAR Part 43 — Contract Modifications and the Changes clauses at FAR 52.243. This page is general information, not legal advice; significant disputes warrant qualified government-contracts counsel.