Every time a new project lands in my inbox, the same question comes up first: do we go fixed price or bill by the day? It sounds like a simple call. It's not. I've seen agencies lose serious money on fixed-price projects they'd underestimated, and freelancers refuse time-and-materials out of fear when it was exactly the model that would have protected them.
What's really at stake with each model
Fixed price means you sell a result at a set cost. Clean, predictable for the client. But every hour over your estimate comes straight out of your margin. Time and materials flips the risk: the client carries the budget uncertainty, but the relationship gets tense fast if the invoice runs higher than expected.
We switched two-thirds of our projects to fixed price in 2023. Six months later we'd absorbed the equivalent of 14 unbilled days on a single client. Fixed price is great -- when you truly control the scope. Which is rarely the case with enterprise clients. -- Lucas R., co-founder, UX agency
When fixed price actually works
Fixed price works when you've delivered the exact same type of project at least three or four times before. Not "roughly similar" -- the same. A Webflow site for a law firm, done seven times in eighteen months? You can quote a fixed price with confidence and know exactly where your margin lands.
It also works well for document-based deliverables: SEO audits, benchmark reports, content strategy. Scope is locked upfront and client review rounds are capped in the contract. Agencies that industrialise these processes typically gain 15 to 25% more net margin compared to billing the same work by the day.
When time and materials protects you
Unstable backlog? Client who doesn't know what they want yet? Digital transformation, app development, SI overhaul -- putting a fixed price on any of these is setting yourself up for the most classic scope creep in agency history. Time and materials lets you start, learn, and adjust. That's what it's built for.
There's a less obvious case too: senior, well-structured clients who manage projects rigorously internally. These clients prefer paying exactly what was consumed rather than feeling overcharged on an opaque fixed quote. With this profile, I've seen commercial relationships last 40% longer on time and materials.
Time tracking in T&M: your credibility is on the line
In a time-and-materials model, your entire credibility rests on the quality of your time reports. Approximate timesheets reconstructed every Friday evening will get you into conflict fast. Tools like Clynt let you log time continuously, attach it to projects, and share a readable report with the client through a dedicated portal. That changes the trust dynamic completely.
The hybrid model: a strategy, not a compromise
Some agencies run a fixed-price scoping phase, time-and-materials for production, then fixed price again for acceptance and delivery. The scoping phase -- typically between 1,500 and 4,000 euros -- lets them enter the project safely and build a precise enough backlog to estimate what comes next. It also qualifies the client: someone who balks at paying for scoping will struggle to manage a long T&M project.
Five criteria to pick your model
- Brief quality: detailed and validated = fixed price viable; vague or evolving = T&M required
- Number of client decision-makers: more than 3 = budget at least 20% overrun buffer on fixed price
- Number of comparable past projects: fewer than 3 references = never quote fixed price without a 25% buffer
- Client validation process: no formal sign-off process = T&M is safer
- Project duration: beyond 4 months, unknowns compound and fixed price becomes a gamble
The signal your billing model sends
Agencies that only bill T&M implicitly say they sell time, not expertise. Agencies that lead with fixed price say they master their craft and own the execution risk. The best clients -- those looking for a partner, not just a vendor -- often value fixed price precisely because it commits the agency to a result. Your billing mix sends a message. Make sure it's consistent with the market position you want.
FAQ
Can you switch from fixed price to T&M mid-project?
Yes, but it requires a formal contract amendment and a transparent conversation with the client. The cleanest approach is to anticipate this in the original quote by including a renegotiation clause if scope exceeds a defined threshold, for example 20% additional unplanned days.
Which model is better for a first project with a new client?
If the brief is vague or you don't know the client's working style, start with a small fixed-price scoping phase. It lets you test the relationship, clarify scope, and choose the right model for the rest of the project with real information.
How do I set a daily rate that doesn't undervalue my work?
Start from your real FTE cost: fully loaded salary plus a share of fixed overheads, divided by actual billable days per year (typically 180 to 210). Then apply your target margin. Don't look at competitor rate cards before doing this math -- you risk anchoring to a market that chronically underprices its own costs.
How does Clynt help compare profitability between T&M and fixed price?
Clynt centralises time tracking, invoicing, and per-project costs in one place. Within a few clicks you can see the real margin on each project broken down by billing model, which lets you quickly spot underpriced fixed-price projects or T&M work that's draining resources without sufficient return.