Comparison · Working with contractors
Fixed price vs time and materials
Development work is usually priced in one of two ways. Fixed price: an agreed scope for an agreed amount. Time and materials: you pay for the time actually spent, usually with estimates and regular reporting. Each distributes risk differently between client and contractor, and each suits different kinds of projects.
[ 01 ]
In short
In short
- 01
Fixed price gives budget certainty for a clearly defined scope; changes are estimated separately.
- 02
Time and materials gives flexibility for evolving projects; budget control comes from priorities and reporting.
- 03
Fixed price requires detailed scope upfront; vague scope leads to disputes or padded estimates.
- 04
Time and materials requires trust, transparency and an engaged product owner on the client's side.
- 05
Many projects combine them: fixed-price discovery or first release, then time and materials for improvements.
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Comparison
Side by side
| Criterion | Fixed price | Time and materials |
|---|---|---|
| Budget certainty | High for the agreed scope | Lower; managed by priorities and caps |
| Flexibility | Changes require change requests | Changes absorbed naturally |
| Required upfront detail | High | Moderate |
| Risk of overrun | Mostly with the contractor | Mostly with the client |
| Contractor's incentive | Efficiency within scope | Delivering value per iteration |
| Client involvement | At approvals | Continuous |
| Best for | Well-defined projects | Evolving products, ongoing work |
When fixed price fits
- The scope is clear: a website with defined pages and functions, a specific integration.
- Budget approval requires a fixed amount.
- Requirements are unlikely to change significantly.
Precise scope documents, acceptance criteria and a change process protect both sides. See website contract checklist.
When time and materials fits
- New products where requirements will evolve with user feedback.
- Ongoing development, support and improvements.
- Complex integrations where unknowns are discovered along the way.
Controls: monthly or sprint budgets, prioritised backlog, regular demos and time reports, a cap that requires approval to exceed.
Combined models
- Discovery at fixed price: a short paid phase to define scope precisely, followed by a fixed-price or estimated build.
- Fixed-price first release, then time and materials: certainty for launch, flexibility for improvements.
- Retainer: a fixed monthly volume of hours for support and changes.
Warning signs
- A fixed price quoted without understanding the task — it will either be padded or lead to cut corners.
- Time and materials without regular reporting — budget control is impossible.
- No written change process in either model.
Verdict
Use fixed price when you can describe exactly what you need. Use time and materials when you will learn what you need as you go. For many projects, a fixed-price discovery followed by an appropriate build model gives the best balance.
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FAQ
Frequently asked questions
Which is cheaper?
Neither by nature. Fixed prices include a margin for risk; time and materials costs depend on how scope evolves. Clear scope reduces cost in both.
How are changes handled in fixed-price projects?
Through change requests: each change is estimated and approved before work, adjusting price and timeline.
Can we cap time and materials?
Yes. Monthly caps and approval thresholds keep spending predictable.