Change orders
A change order handles discovered conditions and customer-requested additions: rotten decking found under the shingles, an extra fixture, an upgraded material. It references the original agreement, describes the change, prices it, states its effect on the schedule, and is authorized before the work is done.
Volume matters here — a business doing this well handles change orders in minutes on site, because a change order that takes an hour will be skipped and the work will be given away.
Amendments
An amendment changes the agreement's terms rather than its work: a revised payment structure, a different warranty period, a corrected party name, an extended completion date with new conditions. These are less frequent and more consequential, and they typically warrant the same review and signature process as the original contract.
What never happens
Neither one is handled by opening the signed document and editing it. The executed agreement is a record of what was agreed at a point in time. Changes attach to it; they do not overwrite it. If a document has to be reissued because the terms genuinely changed before execution, the old envelope should be superseded and every prior access invalidated rather than left live.
Choosing between them
- Is the work different? Change order.
- Are the terms different? Amendment.
- Both? Two documents, or one amendment that also restates the scope.
- Is a party different? Amendment, and usually a re-signing.
The legal boundary
Whether a specific modification needs to be signed, whether it requires new notices, and whether it affects lien or cancellation rights depend on your jurisdiction and the contract itself. This page is about the operational distinction — take the legal question to counsel.