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Fixed price vs time and materials: who carries the risk

Fixed price transfers risk to the supplier — who prices it in. Time and materials keeps it with you and rewards discovery. Neither is honest without a clear scope.

Outcomes

  • Fixed price needs a documented specification to be meaningful
  • Time and materials needs a trusted supplier and an engaged product owner
  • Capped time and materials is a workable middle ground
  • Change control matters more than the model chosen
  • Discovery is best paid separately under either model

Problems this solves

Fixed price needs fixed scope

Without detailed scope, the risk premium in a fixed price exceeds what the flexibility is worth.

Time and materials needs trust and visibility

Sprint demos, burn reporting and a change log make it controllable rather than open-ended.

Change requests become adversarial

Fixed price pushes both sides into arguing about interpretation instead of building.

How delivery runs

  1. 01

    Fixed-price discovery

    Discovery itself is fixed price — it is well understood and produces the scope.

  2. 02

    Fixed-price first phase

    Where scope is clear after discovery, phase one is quoted fixed.

  3. 03

    Time and materials afterwards

    Later phases run on measured velocity with a capped monthly spend.

  4. 04

    Written change control

    Every addition estimated and scheduled explicitly, in both models.

Build or buy

Buy something existing when

  • Fixed price for well-defined, self-contained deliverables

Build custom when

  • Time and materials with a cap for evolving products

What moves the price

Scope certainty

The less certain the scope, the larger the risk premium in any fixed price.

Integration unknowns

Third-party systems you do not control are difficult to fix-price honestly.

Change appetite

If you expect to learn and adjust, fixed price works against you.

Where projects go wrong

Fixed price built on a thin brief

Expect quality to absorb the difference; insist on discovery first.

Uncapped time and materials

Always agree a monthly cap and a stop-or-continue review point.

FAQ

Questions buyers ask

Which do you recommend?+

Fixed price when scope is knowable, capacity-based when it is genuinely exploratory. We say which before quoting.

How are changes handled?+

A written change with impact on cost and date, approved before work starts.

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fixed price vs time and materials