Fixed Price vs Hourly: Which One Actually Protects You
Hourly billing sounds fair and flexible. In practice it moves every risk in the project onto the person who understands it least. Here's how to think about it.
Hourly billing is presented as the fair option. You pay for what you use. Nobody pads the estimate. If it takes less time, you pay less.
That is the theory. In practice, time-and-materials moves nearly every risk in the project onto the party least equipped to carry it: you.
What you're actually agreeing to
When you sign an hourly contract, you agree to pay for however long the work takes, as judged by the people doing it.
Consider what that means when something goes wrong. A developer misunderstands a requirement and builds the wrong thing for a week. Who pays for the week? You do. A library turns out not to work as documented, costing three days. You pay. Someone new joins the team and needs a week to come up to speed. You pay for that too.
None of those are necessarily anyone acting in bad faith. They are ordinary software problems. The question is only ever who absorbs them, and under hourly the answer is always you.
The incentive problem
The awkward truth about hourly billing is that efficiency reduces the vendor's revenue.
Nobody sits down and decides to be slow. But when the meter runs, thousands of small decisions tilt one way. Is it worth automating this? Should we spend two days refactoring? Should we build the simple version or the thorough one?
Under fixed price, every one of those questions has an obvious answer, because finishing early is the vendor's gain. Under hourly, the incentive quietly points the other way.
What fixed price actually requires
Fixed price is not simply a number attached to a vague brief. That combination produces the worst outcome available: a vendor discovering mid-build that they underpriced, and then cutting quality to survive.
Real fixed price requires three things:
A real specification. Written before pricing, detailed enough that both sides can tell whether a given thing is in or out. This is why we run a discovery week. Not as a formality, but because you cannot fix a price on something you have not defined.
An explicit exclusions list. What is not included, stated plainly. This section prevents more disputes than any other part of a contract.
Change control that works. Changes are normal. The rule is only that a change is quoted and approved before it is built. No surprises on the invoice.
If a firm offers you fixed price without doing that work first, they are either guessing or planning to make it back in change orders.
Where hourly is genuinely right
Some work cannot be fixed-priced honestly:
Open-ended research. "Find out whether this is even possible" has no definable endpoint.
Ongoing maintenance. Bugs and small changes arrive unpredictably. A monthly retainer is the honest structure. A hybrid, really: fixed monthly price for an agreed capacity.
Staff augmentation. If you want a developer embedded in your team taking direction from your manager, you are buying time. Fixed price makes no sense there.
The line is roughly: defined outcome → fixed price. Undefined outcome → hourly, with a cap.
Questions worth asking a vendor
- What happens if it takes longer than you estimated? Under fixed price, nothing. That is their problem. Watch how quickly they answer.
- What's explicitly not included? A vendor who cannot answer this has not thought about scope.
- What's your change process? "We'll just add it to the invoice" is the wrong answer.
- Can I see the specification before I commit to the price? If price comes before spec, the price is a guess.
How we do it
We run a discovery week, produce a written specification, and quote a fixed number against it. The spec is yours whether or not you continue. You can take it to another firm, and some people do.
After you sign, the number does not move. If we misjudged the effort, that is our problem, not a change order. If the scope genuinely changes because you want something different, we price it before we build it.
That arrangement is only possible because of the discovery week. Skip that step and fixed price becomes a fiction that hurts somebody, usually both of us.
Want a fixed number for your project? Start with one call. You'll leave with a scope and a price, or an honest no.