Procurement teams love fixed-price contracts. They're predictable, they're easy to budget, and they shift risk to the vendor. The problem is that they almost always fail in software — and the failure mode is the same every time.
The structural reason fixed-price fails
Software fixed-price contracts assume scope is knowable up front. In about 5% of engagements, it actually is — small features, well-defined integrations, replatforms with no business-rule changes. In the other 95%, scope discovery happens during build. The vendor has two options:
- Absorb the scope. Margins evaporate. Quality suffers. The team gets pressured to cut corners. The relationship turns adversarial.
- Bill change requests aggressively. The CR process becomes the project. Every meeting is a negotiation. The vendor wins on paper and loses the renewal.
Fixed-price contracts don't reduce risk. They concentrate it in the change-request process.
Three structures that work
1. Fixed-price with a defined-scope wedge
Use fixed-price only for the part of the work where scope is genuinely knowable. A typical wedge: discovery, architecture, and integration audit. Everything downstream is T&M with a hard cap and a transparent burn-rate dashboard. This works because the parties have already aligned on scope before the variable-cost work begins.
2. T&M with a budget cap and named team
The vendor cannot exceed a defined dollar cap. The team is named in the SOW with CVs attached and cannot be substituted without your approval. Daily/weekly burn is published in a shared dashboard. You get the predictability of fixed-price (cap) with the scope adaptability of T&M.
The catch: this requires real engineering managers on your side to monitor. If you're going to set this and forget it, fixed-price might be safer.
3. Outcome-based with a milestone schedule
Payment tied to validated outcomes — not deliverables. “Order orchestration handles all six channels with <200ms p99 latency” rather than “feature X delivered.” This requires more upfront work to define what good looks like, but once defined, it aligns vendor incentives with yours better than any other structure.
Outcome-based works best when there are 2–4 clear success criteria. It works poorly when there are 25 small features — the overhead of defining each one as an outcome consumes the savings.
The questions to ask before signing
- If scope expands by 20%, what happens to price and timeline? (Get this in writing.)
- Who owns the integration risk if a third party causes a delay?
- What's the change-request turnaround time? Anything over 5 business days kills momentum.
- If the named team gets reassigned, what's the SLA on replacement?
- Is there an out clause — and what does it cost?
What we do
For most engagements we offer all three structures and recommend based on scope clarity. Greenfield platforms get phased fixed-price-then-T&M. Modernization gets dedicated team retainer. Replacement projects get outcome-based. We almost never quote fixed-price for the whole engagement — and when a client insists on it, it's usually a sign that the scoping work hasn't been done yet.
If you're evaluating quotes from us or from competitors, we're happy to walk through the commercial structure on a 30-minute call. Sometimes the answer is “our quote is the wrong structure for this work” — and we'll say so.