The Fixed Fee That Quietly Lost Its Margin
When you bill a fixed fee, WIP is the only thing telling you whether the job made money. Here's how to watch margin before it's gone.
Fixed-fee pricing was supposed to make billing simple. You agree a number, you do the work, you send the invoice. No timesheets to argue over, no surprises for the client. And for the client, that's usually true.
For the firm, it's a different story. A fixed fee doesn't remove your cost — it just hides it. The hours still happen. The scope still creeps. The junior still redoes the reconciliation twice. The only difference is that none of it shows up on the invoice, so none of it gets noticed until you look back at the year and wonder why a full book of work produced a thin result.
The margin lives in the WIP, not the invoice
On a time-and-materials job, overservicing is visible: your bill goes up, and either you wear it or the client queries it. On a fixed-fee job, overservicing is invisible by design. The invoice stays the same no matter how many hours go in behind it.
That means the only place your margin is actually being decided is your work-in-progress. WIP is the running record of effort against a job — the hours, the stages, the who-did-what. On a fixed fee, comparing WIP to the agreed price is the single most important number you're probably not looking at.
Consider a $2,200 annual compliance job you priced assuming ten hours of work. If your team logs eighteen hours because the client's records arrived in pieces and the file needed rebuilding, you haven't just done extra work. You've cut your effective rate almost in half. And because the fee never moved, nothing prompted you to notice.
Why "we do fixed fee so we don't track time" is a trap
It's a common line, and it sounds efficient. If the fee is fixed, why bother logging hours? The problem is that abandoning time tracking doesn't make the cost disappear — it just makes it unmeasurable.
Without a record of effort, you can't answer basic questions:
- Which of your fixed-fee jobs are actually profitable?
- Which client always takes twice as long as you priced for?
- Which service line looks busy but earns nothing?
- Is a particular staff member's job taking longer because of complexity, or because of how it's being done?
You don't track time on a fixed-fee job to bill it. You track it to price the next one correctly and to catch the jobs bleeding margin while you can still do something about them.
The scope you priced isn't always the scope you did
Most fixed-fee erosion isn't dramatic. It's a series of small yeses. An extra query answered. A payroll question handled because it was quicker than saying no. A set of records tidied that the client was supposed to provide clean. Each one feels too minor to raise. Together they turn a profitable engagement into a break-even one.
This is where the fixed fee and the engagement letter have to talk to each other. If your letter says the fee covers a specific scope, then work outside that scope is a variation — a conversation and, potentially, an additional fee. But you can only have that conversation if you can see the extra work stacking up against the agreed price in real time. If you notice it at year-end, the moment has passed and the goodwill of raising it is gone.
What to watch, and when
The point of monitoring WIP on fixed-fee work isn't to obsess over every six minutes. It's to catch the jobs drifting past their budget while there's still a decision to make. A few practical habits:
- Set a budget on the job, not just a fee. Record the hours you assumed when you priced it. Now you have something to measure against.
- Review WIP against budget mid-job, not at the end. A job at 80% of budgeted hours with half the work done is telling you something now — not in three months.
- Flag the pattern, not just the instance. One job over budget is noise. The same client over budget three years running is a repricing conversation.
- Separate genuine scope changes from inefficiency. A file that took longer because the client changed structures is a variation. A file that took longer because of rework is a training or process issue. Both matter, but you fix them differently.
Bringing it into one view
The reason so many firms fly blind on fixed-fee margin is that the pieces live in different places. The agreed fee is in the engagement letter. The effort is in a timesheet nobody reconciles. The invoice is in Xero. The client's file is somewhere else again. To see whether a job made money, someone has to stitch all of it together manually — so nobody does.
This is exactly the gap good accounting client management software should close. In a system like Finye, the job carries its own budget, its own logged time and its own WIP, and it sits alongside the engagement letter that defined the scope. You can see, on a single job, what you agreed to do, what it's actually taken, and how that compares to the fee — before you raise the invoice, not after. Because Finye syncs invoicing two ways with Xero, the billing side stays connected to the practice side rather than living in a separate world.
The value isn't the timesheet for its own sake. It's that fixed-fee work stops being a black box. You bill the agreed fee with confidence because you can see the job earned it — or you catch the erosion early enough to reprice, rescope, or fix how the work gets done.
The number worth knowing before you renew
Every fixed-fee engagement comes up for renewal. That's your one clean moment to correct a price that's stopped working. But you can only take it if you know the truth about the job — how much effort it really consumed, and what that did to your margin over the past year.
A firm that tracks effort against fixed fees walks into renewal season with evidence. It knows which clients to reprice, which to keep as they are, and which services to reshape. A firm that stopped tracking because "the fee is fixed" walks in with a hunch. The fee stays simple for the client either way. The difference is whether it stays profitable for you.