Only a written modification changes the deal
A federal contract is the document, not the relationship. Scope, price, schedule, and terms only change when the contracting officer issues a written modification, sometimes called a mod, and both sides sign it. A COR asking you to just add a feature, a program manager requesting a favor, or your own instinct to be helpful, none of it changes the contract. Only the CO can, and only in writing.
Option years are the government's choice, not yours
Many contracts are structured as a base period plus option years, additional periods the government may exercise at its own discretion, usually at pre-priced or re-negotiated rates set in the original contract. Exercising an option is the government's unilateral right, not a negotiation you initiate. Performing well and staying easy to work with is the actual lever you have; there is no formal process for asking the government to pick up your option early.
The constructive change trap
A constructive change happens when someone directs you, verbally or through informal email, to do something beyond the contract's scope, and you do it without a written mod. You may have a legitimate claim for extra payment afterward, but proving it means reconstructing intent after the fact, against a government that never signed anything. It is a slow, expensive way to get paid for work you already gave away for free. The safer habit: when a request falls outside what the contract describes, say so plainly and ask for a modification before you start, not a claim after you finish.
Pricing and negotiating a mod
When a mod is warranted, price it the way you priced the original bid, real labor hours, real materials, a documented basis, not a round number that feels fair. Keep your cost buildup even for small mods, because a pattern of undocumented pricing is exactly what an auditor questions later; see accounting a government auditor will accept. Negotiate the way you would any contract change: know your walk-away number, put your reasoning in writing, and remember the CO has to justify the price to their own file too, so a well-documented ask is easier for them to approve.
Read every mod before you sign it
Modifications can be as small as an address correction or as large as a full re-scope. Read the whole document, not just the summary line, and confirm it says what you agreed to in conversation. Verbal agreements about a mod are exactly as binding as verbal agreements about the original contract, which is to say, not binding at all until they are in writing and signed.