Fixed Price vs Time and Materials vs Retainer
· 5 min read · TintSol
The three software development pricing models
- Fixed price (fixed scope): the supplier commits to delivering an agreed scope for an agreed price, usually paid against milestones. Changes are handled through change requests.
- Time and materials: you pay for the hours actually worked, often reported weekly or monthly. Scope can change freely; so can the bill.
- Retainer or dedicated development team: a recurring monthly fee for an agreed team or block of capacity, with priorities set by you as you go.
The main difference between them is who carries the risk of the unknown. With fixed price, the supplier carries estimate risk. With time and materials, you do. With a retainer, the risk is shared: cost is predictable each month, and you decide what the capacity is spent on.
Side-by-side comparison
| Factor | Fixed price | Time and materials | Retainer / dedicated team |
|---|---|---|---|
| Budget certainty | High for agreed scope | Low unless capped | High per month |
| Flexibility to change scope | Through change requests | High | High within capacity |
| Upfront definition needed | Detailed | Light | Light; priorities set continuously |
| Who carries estimate risk | Supplier | Client | Shared |
| Your management effort | Mostly at milestones | Ongoing, to control hours | Ongoing, to set priorities |
| Best fit | MVPs, defined builds, clear deadlines | Research, prototypes, unclear requirements | Live products, continuous improvement, long roadmaps |
When each model fits
Match the model to the stage of your product rather than to habit.
- Fixed price works when you have done discovery, know the features of the first release and need a firm budget for investors or a board.
- Time and materials works for short, exploratory pieces of work where defining the scope is the work, such as technical investigations.
- A retainer works once a product is live and you want a stable team that knows the codebase, ships improvements steadily and handles maintenance.
Many products move through the models over their life: a fixed-scope first release, followed by a retainer to keep improving it.
Two questions usually decide it. First, could you write down the features of the next release today and still agree with that list in a few months? If yes, fixed price is realistic. Second, will there be meaningful work on this product every month for the foreseeable future? If yes, a retainer or dedicated team is likely to serve you better than a series of separate projects.
What a good contract includes for each model
The pricing model shapes the contract. Whichever you choose, make sure these points are written down.
- Fixed price: a scope document with assumptions and exclusions, milestone deliverables with acceptance criteria, a change-request process and a warranty period after launch.
- Time and materials: rates per role, a monthly cap or approval threshold, regular timesheet reporting and the right to review progress against spend.
- Retainer or dedicated team: the team composition and capacity, how priorities are set, notice periods for scaling up or down, and documentation standards.
- All models: intellectual property assignment on payment, confidentiality, data handling, repository access from day one and a handover process if the engagement ends.
Pitfalls and how to avoid them
| Model | Common pitfall | How to avoid it |
|---|---|---|
| Fixed price | Vague scope leads to disputes and a stream of change requests | Do discovery first; list assumptions and exclusions in the contract |
| Fixed price | Supplier cuts corners to protect margin | Define acceptance criteria and a warranty period |
| Time and materials | Budget drifts without anyone deciding to spend more | Set a monthly cap and review burn against progress |
| Retainer | Capacity is used on low-value work | Keep a prioritised backlog and review outcomes monthly |
| Retainer | Team changes erode knowledge | Agree team stability and documentation standards |
How TintSol works
TintSol offers two of these models: fixed-scope projects with defined milestones, and ongoing retainers. We do not sell open-ended time and materials. For a new product we usually recommend a fixed-scope first release, then a retainer once it is live and the roadmap depends on what users do.
There is no public rate card; every engagement is quoted after we read a brief. Send yours through the contact page and you will hear back within one business day.