Fixed Price vs Time & Materials: How Should You Pay for Software Development?

When an agency sends a proposal, the pricing model can matter as much as the price. Two quotes for the same project can carry completely different risks depending on whether you're paying a fixed amount, paying for hours, or paying for a team. Here's how each model actually works, what it quietly costs you, and how to pick.

The three main models

Fixed price

One agreed price for an agreed scope, usually paid in milestones. You know the number up front. The hidden cost: the agency carries the risk of underestimating, so a sensible agency adds a buffer to cover it. And because scope is locked, every change becomes a formal change request, which can create friction exactly when you learn the most about what users need.

Time and materials (T&M)

You pay for the hours actually worked at an agreed rate, usually billed weekly or monthly. Scope can change as you learn. The hidden cost: the final bill isn't known up front. Without caps and visibility, budgets can drift.

Dedicated team or retainer

You pay a monthly fee for a set team or a block of hours. Best for ongoing product development and maintenance. The hidden cost: you're paying for capacity, so you need a steady backlog of work, and someone on your side to prioritise it.

Side-by-side comparison

	Fixed price	Time & materials	Dedicated team
Budget certainty	High	Low–medium (use caps)	High per month
Flexibility to change	Low	High	High
Who carries estimate risk	Agency (priced in)	You	You
Upfront spec needed	Detailed	Light	Ongoing backlog
Best for	Well-defined MVP or phase	Evolving products, unclear scope	Long-term product work

Which model fits your project?

• Choose fixed price when the scope is genuinely clear: a well-written PRD, known integrations, and a defined first release.
• Choose T&M when you're still discovering what users need, or when integrations and third parties introduce unknowns.
• Choose a dedicated team once the product is live and you have a continuous roadmap.

The hybrid that works for most founders

In practice, the most founder-friendly approach combines them:

1. A short, fixed-price discovery phase to turn the idea into a clear scope, wireframes, and estimate.
2. Fixed-price milestones for the well-defined MVP, each paid on delivery of working software.
3. T&M or a monthly retainer after launch, when priorities change weekly based on real user feedback.

This gives you budget certainty where scope is clear, and flexibility where it can't be.

How to protect yourself under any model

• Tie payments to working software, not to time passing or documents delivered.
• Ask for a monthly cap on T&M work, with approval needed to exceed it.
• Get weekly visibility: hours used, what was built, what's next.
• Agree how changes are priced before the first one comes up.
• Watch the feature creep. Every addition costs more than it looks. Here's why.

For typical budget ranges, see our 2026 app cost guide, and before signing with anyone, run through these 12 questions to ask a development agency.

Not sure which model fits?

We work fixed-price, milestone-based, and on retainer, and we'll recommend the one that fits your stage rather than the one that suits us. Explore our custom software development service, or share your project brief for an itemised estimate.