The Write-Off You Never Decided: Where Margin Quietly Leaks
Most write-offs aren't decisions — they're what's left when unbilled time ages out. Here's how to catch WIP before it becomes a silent discount.
Ask a practice owner about their write-offs and you'll usually get a shrug and a rough percentage. Ask where those write-offs came from — which jobs, which clients, which decisions — and the answers get vague fast. That vagueness is the problem. In most firms, the majority of write-offs aren't decisions anyone made. They're what's left over when time sits in WIP long enough that nobody feels comfortable billing it.
A write-off should be a choice: we did this work, and for a defensible reason we're not charging the client for all of it. What actually happens is quieter and more expensive. Time gets logged, the job wraps, weeks pass, and by the time someone looks at the WIP, the detail is stale, the story is forgotten, and writing it off feels easier than justifying it. That's not a pricing decision. That's margin leaking through a gap in your process.
Why unbilled time turns into a discount
The gap runs from the moment work is done to the moment it's invoiced. The longer that gap, the more your realisation rate erodes — and it erodes for predictable reasons.
- Memory decay. The person billing wasn't the person doing the work, or was, but three weeks ago. The nuance that would justify the hours is gone. So the hours get trimmed.
- Confidence decay. Fresh WIP is easy to defend. Ageing WIP invites doubt. "Did we really spend six hours on that?" Doubt always rounds down.
- Client-relationship drift. Bill a client promptly and the value is obvious. Bill them two months late and it feels like you're chasing money for work they've half forgotten — so you soften the number to keep things smooth.
- Batch guilt. When WIP piles up and you finally bill in a big sweep, the total looks alarming even when it's fair. The instinct is to knock it down to something "reasonable."
None of these is a considered write-off. They're all symptoms of time that aged before it was billed. And they compound: a firm running at 85% realisation isn't necessarily overservicing — it may just be billing slowly.
The number nobody reviews on time
Every practice tracks time. Fewer track WIP as a living balance, and fewer still review it while it's still fresh enough to act on. The WIP ageing report — the same tool you'd use to chase overdue debtors — is the single most useful lens here, and it's the one most firms only glance at once a quarter.
Run it weekly and the pattern jumps out. You see which jobs are carrying time that should already be invoiced. You see the client who always has three months of WIP sitting against them. You see the staff member whose hours reliably get written down — which might be a training issue, a scoping issue, or a signal you're underpricing that service line entirely.
What you're really looking for is the decision point: the moment a piece of WIP shifts from "bill it in full" to "we'll never get that back." That point almost always arrives earlier than people think. If you review WIP monthly, you're already past it on half your jobs.
Close the gap between work and invoice
The fix isn't heroic. It's structural. You want billing to happen close to the work, so the decision to write off — if you make it — is a genuine call, not a default.
Bill against the job, not the calendar
Monthly billing runs create the exact batch problem that drives write-offs. Where the work has natural completion points — a return finalised, a set of accounts signed off, an advisory piece delivered — bill at that point. In practice management software that ties time to specific work items, the WIP for a job is right there when it's marked complete. That's the moment to raise the invoice, while the detail is fresh and the value is obvious to everyone.
Make WIP visible to the person doing the work
Realisation improves when the people logging time can see what that time is worth and whether it's been billed. When WIP is a hidden back-office number, staff have no feedback loop. When it's visible against the job they're working, overservicing gets caught early and scope conversations happen before the overrun, not after.
Set a WIP age threshold — and treat it as a trigger
Pick a number. Fourteen days, thirty days, whatever fits your cycle. Any WIP older than that gets a decision this week: bill it, or explain why not. The point isn't the number itself. It's converting a passive drift into an active choice. Finye's boards and WIP reporting let you surface ageing time against each work item, so the review is a five-minute scan rather than an archaeology project.
When a write-off is the right call
To be clear: not every write-off is a failure. Sometimes you overserviced because you were learning a new client. Sometimes a fixed-fee engagement ran long and eating the difference is the deal you signed up for. Sometimes goodwill on a small overrun buys loyalty worth far more than the hours.
The difference is that those are decisions. You know why you made them, you can point to the reasoning, and you can decide whether to price differently next time. The write-offs that hurt are the ones you can't explain — the ones that just showed up in the numbers because time aged out of usefulness before anyone billed it.
What this looks like in a running practice
A firm that's closed this gap has a few things in common. Time is logged against specific jobs, not a vague weekly bucket. WIP is reviewed weekly, not quarterly. Invoices go out on completion, so the gap between work and bill is measured in days. And when a write-off happens, someone chose it and can say why.
Get there and your realisation rate stops being a mystery. You'll find you weren't overservicing as much as you feared — you were just billing too slowly and paying for it in quiet discounts. Client accounting software that keeps time, WIP and invoicing in one connected view is what makes the review fast enough to actually do every week. That's the whole game: not tracking more, but deciding on time, while the WIP is still worth billing in full.