Fixed-price usually fits a web project when its scope and acceptance criteria are clear enough to estimate. Time-and-materials (T&M) is more adaptable when requirements or technical work may change, but leaves the buyer with less certainty about the final bill. Choose by matching the payment structure to what is known, then put scope changes, approvals, reporting, and budget limits in writing.
How the two contract types allocate cost risk
| Decision point | Fixed-price | Time-and-materials (T&M) |
|---|---|---|
| What payment follows | An agreed price for defined work. The provider takes greater responsibility for costs exceeding its price assumptions. | Agreed rates for labor and, where applicable, materials. Total spend depends on effort used. |
| When it tends to fit | Deliverables, dependencies, and acceptance criteria are clear enough to estimate credibly. | Requirements, technical approach, or duration remain uncertain and may evolve during delivery. |
| Buyer’s main exposure | The buyer may owe the agreed price even if the result feels less valuable than expected; omitted work or later changes may require repricing. | The total cost is uncertain, so the buyer must monitor effort, progress, and remaining budget. |
| Provider’s main exposure | Underestimating effort or absorbing additional work needed to meet the defined obligation. | Work may be limited by the buyer’s budget or approvals, and the provider must maintain agreed billing records. |
The U.S. Federal Acquisition Regulation (FAR) describes fixed-price contracts as placing maximum cost risk and responsibility on the contractor, while distinguishing T&M and labor-hour arrangements as payment based on effort rather than results. That is federal contracting language, not a rule that automatically determines a private agency agreement. See FAR Subpart 16.2 and FAR Part 16.
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Which model is better for a web development project?
Neither is inherently better. A useful test is whether the work can be described and accepted before development begins. The FAR says contract type should be selected deliberately for the government’s interest; the U.S. Digital Service’s TechFAR Handbook notes that agile software development is not limited to fixed-price arrangements and discusses T&M or labor-hour contracting when requirements cannot be defined or costs estimated sufficiently. These are public procurement sources, but the underlying decision is useful for private projects too. See FAR Subpart 16.1 and the TechFAR Handbook.
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Fixed-price is more workable when both sides can identify what will be delivered, what inputs the client must provide, and how completion will be judged. A defined website build might specify a set of page templates, integrations, responsive behavior, content responsibilities, and acceptance tests. A single agreed price does not mean every later wish or omitted requirement is included; the written scope and change procedure determine what is covered.
Choose T&M when important details remain unknown
T&M can make sense for discovery, uncertain integrations, evolving product requirements, or iterative work where the next tasks depend on what the team learns. It allows the work to adapt without pretending the full effort is knowable up front. But hourly billing does not, by itself, cap total spend. A 2022 U.S. Government Accountability Office report describes T&M and labor-hour contracts as riskier in federal procurement because billing by the hour can create incentives to expend more hours; it also discusses periodic review and converting understood portions to fixed-price. This is a procurement risk observation, not evidence that every T&M provider works inefficiently. See the GAO report.
What to define in a fixed-price agreement
Fixed pricing works only as well as the definition of the work and the way changes are handled. UK Cabinet Office guidance likewise links fixed-price arrangements to a clear specification and appropriate allocation of delivery risk. For a private web engagement, translate that principle into terms both sides can inspect and test; it is not a universal legal checklist. See the UK Cabinet Office pricing guidance.
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- Deliverables: Name pages, templates, features, integrations, environments, documentation, and any handover work included.
- Acceptance: State testable criteria, who reviews the work, how long review takes, and how defects or rejected work are addressed.
- Assumptions and exclusions: Clarify supported browsers, content migration, accessibility targets, third-party costs, hosting, maintenance, and what is expressly outside the price.
- Dependencies: Assign responsibility for content, credentials, design assets, approvals, and vendor access; explain how delays affect dates or price.
- Milestones and payment: Tie payments to identifiable work or acceptance events and state any conditions that apply.
- Change procedure: Require changes to be written, assessed for price and schedule impact, and approved by authorized people before work begins.
How to control costs under T&M
A T&M agreement should make the work and its cost visible frequently enough for the client to make decisions before the budget is exhausted. GAO’s discussion of periodic review supports treating T&M as an actively managed arrangement rather than a blank cheque.
- Set rates by role: List the roles, hourly or daily rates, and rules for expenses or materials. State whether rates can change and under what conditions.
- Require time records and reports: Agree on timesheet detail, reporting cadence, work completed, work remaining, risks, and forecast spend.
- Use approval thresholds: Identify who can authorize work, whether approval is required above a stated estimate, and whether unapproved hours are billable.
- Set a ceiling or stop-work trigger: State whether there is a not-to-exceed amount, what happens when it is reached, and who can authorize additional work. A ceiling only controls spend if the contract says what occurs at the limit.
- Schedule review points: At regular intervals, compare actual spend with the estimate, reprioritize tasks, and decide whether a well-understood portion should move to a fixed price.
Can a project combine fixed-price and T&M?
Yes. Contract frameworks allow different types or combinations where appropriate, and UK guidance treats pricing and risk allocation as design choices rather than a single formula. For a website, a practical option is to use T&M for a bounded discovery phase, then agree fixed prices for increments whose scope and acceptance criteria are understood. This is an application of those principles, not a prescribed procurement formula. See FAR Subpart 16.1 and the UK Cabinet Office guidance.
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For the discovery stage, define its goals, duration or budget limit, expected outputs, and the decision point for the next stage. Those outputs might include prioritized requirements, technical findings, and estimates for delivery increments. Do not treat a discovery estimate as a binding fixed price for later work unless the parties expressly agree to that pricing and scope.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Questions to settle before signing
- What exactly is included, and how will completion or acceptance be determined?
- Who supplies content, access, assets, approvals, and third-party services—and how do delays affect delivery?
- How are changes documented, priced, prioritized, and approved before work starts?
- For T&M, which roles and rates apply, how often will the client receive reports, and who approves additional work?
- Is there an estimate, spending cap, or stop-work trigger, and who can authorize work beyond it?
- Who owns custom code, designs, and documentation, and what happens to them if the agreement ends early?
Payment structure alone does not answer ownership, termination, or other contract questions. The contract and applicable governing law control; public-sector guidance cited here is context, not private legal advice.
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