You can’t write a fixed-scope, fixed-price contract for work whose point is to change the scope as you learn. Yet many agile engagements still arrive wrapped in exactly that kind of paper. The contract and the method pull in opposite directions, and the people in the middle pay for it.

Because we are a consulting firm, we should be candid: how you pay us changes how we behave. Here are the common options and what each does to incentives.

Time and materials

Time-and-materials (T&M) is the default for agile transformations and coaching, and for good reason. The scope is hard to know in advance, and the client wants flexibility. The risk is plain. The supplier earns more when the work takes longer, and the client carries all the uncertainty. A well-run T&M engagement works anyway, but it needs visible outcomes, not just hours.

Capped time and materials

A cap sets a ceiling on spend and keeps the flexibility below it. It gives finance a number to approve. The danger is that the cap becomes a fixed price in disguise: the team races to hit the scope the cap was based on, or the supplier quietly cuts corners as the ceiling nears. Treat the cap as a budget checkpoint where both sides review progress and decide whether to continue, not as a target to consume.

Fixed price per iteration

Here the client pays a set amount for each iteration of a stable team. Cost is predictable, scope stays flexible, and the supplier has little reason to pad. The weakness is that “a team for a sprint” can drift into paying for effort rather than results. Pair it with a clear definition of done and a working demo at every review.

Fixed budget, flexible scope

The client fixes the total and the end date, and the team delivers the highest-value items first. The client can stop early if the remaining backlog isn’t worth the money. This shares risk most fairly, but it demands a client who prioritizes honestly and a supplier who is willing to say “this won’t fit.” It also makes procurement teams uneasy, because “what will I get?” has no one-line answer.

Keeping trust and accountability

Whichever model you choose, a few habits matter more than the pricing formula:

• Define outcomes, not only activities, and review them at each iteration.
• Include a way out: either party can end the engagement with short notice, so neither feels locked in.
• Share the backlog and the progress data with the client, so nothing depends on our say-so.
• Agree up front how changes in scope, team size, and priorities are handled.

Picture a retailer that signs a capped T&M contract to coach six teams. Halfway through, the cap is 70% spent and two teams are still struggling. A good contract triggers a conversation about changing the plan, not a dispute about who overran.

Contracts won’t create trust, but they can make it cheaper to extend. Before you sign your next agile engagement, ask what behavior the payment model rewards, and fix the answer if you don’t like it.