Before scope, before stack, before timeline — you choose an engagement model. It decides who carries the risk when reality diverges from the plan, and it quietly determines your final bill. There are three common ones.
Fixed-price
You agree a scope and a price up front. Best when the scope is genuinely well understood — a defined integration, a redesign, a clear MVP.
- ✅ Predictable budget; vendor carries delivery risk.
- ⚠️ Every change is a change-order. Fixed-price work is most exposed to the 27% average overrun when scope shifts — and software scope almost always shifts.
Time-and-materials
You pay for time spent at an agreed rate. Best when the path isn't fully known — discovery work, evolving products, R&D.
- ✅ Maximum flexibility; you steer continuously.
- ⚠️ You carry the budget risk, so it demands a trustworthy partner and tight communication.
Dedicated team / staff augmentation
You retain a team (or specific engineers) for a monthly fee; they work as an extension of yours. Best when you have ongoing work and want continuity and control.
- ✅ Deep product knowledge compounds; you direct priorities sprint to sprint.
- ✅ Avoids the hidden cost and 30%+ replacement risk of in-house hiring while keeping near-employee control.
- ⚠️ Only pays off with a real, continuous backlog.
A simple way to choose
- Scope is fixed and clear → fixed-price.
- Scope is unknown or evolving → time-and-materials.
- Work is ongoing → dedicated team.
Many engagements change shape over time — start with one engineer on T&M to prove fit, then scale into a dedicated squad once the backlog is real. The contract should flex with you, not trap you.
Pick the model that puts risk where it's best managed — with whoever controls the scope.
Not sure which fits your situation? Tell us how your work is shaped and we'll recommend a model honestly — even when it's the smaller engagement.
Sources
- Acquaint — Software budget overrun statistics
- Inop — The true cost of a bad hire in 2026