Fixed Price or Time and Materials for a Web or App Project?

Short answer: Fixed price suits a project whose scope you can describe precisely before work starts, such as a brochure website or a clearly specified feature. Time and materials suits work where you'll learn as you go, like a new app or an integration with unknown systems. Fixed price moves cost risk to the developer, who usually prices that risk in, while time and materials keeps cost risk with you but lets the project change course cheaply. Many good projects combine them: a small fixed-price discovery phase, then fixed-price milestones or a capped time-and-materials budget.

How each model works

Fixed price

You agree on a defined scope and a total price, usually paid in stages. The Project Management Institute describes fixed-price contracts as giving the buyer a defined cost without overruns, though the initial price may be higher to account for risks and unknown factors. PMI also warns that if the product isn't well defined, both parties are at risk: the buyer may not get what they wanted, and the seller may face extra costs.

Time and materials (T&M)

You pay for actual hours worked at agreed rates, plus any costs such as licenses. PMI notes that T&M is useful when scope is difficult to define and protects the seller from cost overruns, while the buyer carries the risk of costs escalating.

Comparison

How risk really shifts

Fixed price doesn't remove risk; it moves it and puts a price on it. A developer quoting fixed price must guess how long unclear things will take, and a sensible one adds a buffer. If the guess is generous, you overpay. If it's tight, the developer has an incentive to deliver the narrowest reading of the spec, push back on every clarification, or cut corners on what you can't easily see, such as testing and documentation.

T&M is honest about uncertainty, but it needs you to steer. Without regular reviews and a visible burn rate, a T&M project can quietly double. The manifesto that started the agile movement values "customer collaboration over contract negotiation". T&M works when that collaboration actually happens.

Change requests

Change is normal: you'll see the first version and realise something should work differently. The contract should say how changes are handled.

Under fixed price:

• A written change request describing the change.
• A quoted impact on price and timeline before work begins.
• Your written approval.
• An agreed rate for small changes, so ten-minute fixes don't need a formal quote.

Under T&M:

• A prioritized backlog you control.
• A rule that new work displaces lower-priority work unless the budget increases.
• Weekly or fortnightly reporting of hours used against the budget.

Milestones that protect both sides

Tie payments to things you can check, not to calendar dates:

1. Discovery complete: agreed specification, designs or prototype.
2. Design approved: visual designs signed off.
3. Feature-complete build: everything working on a test site or test build.
4. Acceptance: testing against agreed criteria, issues fixed.
5. Launch and warranty: live, plus a defined period for fixing defects at no cost.

Define acceptance criteria in advance. "Client is satisfied" invites disputes; "the booking form sends a confirmation email and creates a calendar entry" doesn't.

Red flags in quotes

• One line, one number. "Website: $X" with no breakdown of pages, features or integrations.
• Vague scope words: "etc.", "standard", "as needed", "basic SEO" without a definition.
• No mention of content. Who writes copy, sources images, migrates old pages?
• No testing or browser and device coverage listed.
• No warranty period for defects after launch.
• Unclear ownership of code, designs, domain and hosting accounts.
• Fixed price for something no one has specified. A fixed price for "an app like Uber, but for dog walkers" is a guess in a suit.
• T&M with no estimate, no cap and no reporting.
• Large upfront payment with nothing deliverable attached.
• Hosting, licenses and maintenance left out, so the real cost appears after launch.

Hybrid models

Paid discovery, then fixed price

A short fixed-price discovery phase produces the specification, designs and an estimate. You then get a fixed price for the build based on real knowledge, and you can take the specification to another developer if you prefer.

Fixed-price milestones

Break the project into small fixed-price phases. You re-plan after each one, so less is guessed at once.

T&M with a cap

Hourly billing up to a not-to-exceed amount. If the cap approaches, work stops for a joint decision. This keeps T&M's flexibility while limiting exposure.

Fixed budget, flexible scope

You fix the money and the timeline; the developer delivers the highest-priority features that fit. This works well for MVPs where getting something live matters more than getting everything.

Contract tips

• Attach the specification or scope document to the contract.
• State who owns code and designs on payment, and get admin access to every account.
• Define the change request process and small-change rates.
• Define acceptance criteria and the warranty period.
• For T&M: rates per role, reporting frequency, the cap, and notice for rate changes.
• Agree on what happens if either side ends the contract early, including handover of work in progress.

This is general guidance, not legal advice; for larger contracts, have a lawyer review the terms.

FAQ

Which model is cheaper?

Neither by default. Fixed price includes a risk margin; T&M can overrun. For well-defined work, fixed price is often cheaper overall because it limits rework; for uncertain work, T&M avoids paying for risk that may not happen.

Can I switch models mid-project?

Yes, by agreement. A common switch is from T&M during early development to fixed price for a well-understood final phase.

How detailed should a specification be for fixed price?

Detailed enough that two developers would build roughly the same thing: pages, features, user roles, integrations, content responsibilities and acceptance criteria.

What about ongoing work after launch?

That's usually a retainer or T&M arrangement covering updates, security patches and small improvements, priced separately from the build.

Comparing quotes and not sure which model fits your project? Talk it through with us.

Sources

• https://www.pmi.org/learning/library/project-contracts-vendor-buyer-views-7254
• https://www.pmi.org/learning/library/project-contracts-decision-matrix-approach-3277
• https://agilemanifesto.org/