The WIP Ageing Report: Spotting Stale Time Before It's Lost
Unbilled time doesn't age like wine. Here's how to run a WIP ageing review that catches stale work before it turns into a write-off.
Most firms bill on a cycle — end of month, end of job, whenever the partner gets around to it. In between, work in progress quietly piles up. Time gets logged, jobs drag on, and by the time someone raises an invoice, half the story has been forgotten. The client queries a line item. Nobody can remember exactly what the six hours in week two were for. So it gets discounted, or written off entirely.
The single most useful habit for protecting margin isn't stricter time tracking or higher rates. It's treating your unbilled WIP like an ageing debtor: reviewing it regularly, oldest first, and acting on what's gone stale before it becomes unrecoverable.
Why WIP ages badly
Unbilled time has a short shelf life for two reasons.
Recall fades. The value of a WIP entry is only as strong as your ability to justify it. A time note written three days ago is defensible. The same note three months later, when the client pushes back, is a negotiation you'll usually lose. The older the WIP, the deeper the eventual discount tends to be.
Scope creep hides in old WIP. Work that overran the fixed fee, extra queries, that "quick" advice call — these accumulate in WIP without anyone deciding whether they're billable or absorbed. Left unreviewed, the default answer becomes "absorb it," which is a decision made by inertia rather than judgement.
What a WIP ageing report actually shows you
A WIP ageing report groups unbilled time and disbursements by how long they've been sitting there — typically 0–30 days, 31–60, 61–90, and 90+. Instead of one lump sum, you see the shape of your unbilled work.
The pattern usually tells you something specific:
- A large 90+ bucket means jobs are finishing but not being billed, or billing is being deferred while more time gets added.
- WIP concentrated on a handful of clients flags either an under-scoped engagement or a client relationship where nobody wants to raise the bill.
- WIP on jobs marked complete is money you've earned and simply haven't invoiced — the easiest win on the whole report.
The point isn't the number. It's the questions the ageing forces you to ask, client by client, while the answers are still fresh enough to matter.
A monthly 30-minute WIP review
Set aside half an hour at month-end, before you run invoices. Work the report oldest-first, because that's where the risk is highest.
1. Deal with the 90+ column first
Every entry here needs a decision, not a deferral. For each one, pick: bill it now, write it off with a reason recorded, or (rarely) hold it with a specific date to revisit. Anything you can't justify billing at 90 days you almost certainly can't justify at 120.
2. Check completed jobs for trapped WIP
Filter for jobs that are done but still carry unbilled time. This is pure realisation left on the table. In most cases it should be invoiced this cycle — the work is finished, the value is clear, and delay only erodes it.
3. Look for the scope-creep signal
Where a fixed-fee job is carrying WIP well above the agreed fee, flag it. You have two jobs to do: decide whether this instance is billable as a variation, and note whether the scope itself needs adjusting when the engagement renews. Recurring overruns on the same package are a pricing problem, not a billing one.
4. Assign an owner to anything unresolved
WIP that needs a client conversation before it can be billed — a query, a variation, a heads-up call — shouldn't sit on the report indefinitely. Assign it to whoever owns the relationship, with a due date. The report should shrink every month, not just get re-read.
How this connects to the rest of your practice
A WIP ageing review only works if the underlying data is trustworthy, and that comes down to the systems around it. Good client accounting software ties time entries to specific jobs and clients, so ageing WIP maps cleanly back to the work that generated it. When time tracking, jobs and invoicing sit in separate tools, reconciling them monthly becomes its own chore — and chores that are painful don't get done.
This is where consolidating on proper accounting practice management software pays off. In Finye, time is logged against work items on your boards, WIP builds up on the job as staff record their hours, and you can see unbilled time by client, by job, or by age without exporting anything. When you're ready to bill, the WIP converts into an invoice — synced two-way with Xero — so the amount you review is the amount you raise. There's no re-keying and no gap between what you tracked and what you charged.
Because the same platform runs your compliance calendar, recurring jobs and client records, a stale WIP entry isn't an orphan number in a spreadsheet. You can open the job, read the time notes, see who did the work and check whether it sits inside a fixed-fee package or outside it. That context is exactly what makes the bill-or-write-off decision defensible.
Make it a habit, not a rescue mission
Firms tend to discover their WIP problem all at once — usually at year-end, when the write-offs land in a single ugly figure. A monthly ageing review spreads that work out and shrinks the damage, because you're making dozens of small, well-informed decisions instead of one large, poorly-informed one.
The discipline is simple: review oldest WIP first, decide on every stale entry, invoice completed work promptly, and treat repeat overruns as a signal to re-price. Do that consistently and your realisation rate climbs — not because you're working harder, but because far less of the work you've already done quietly disappears before it's billed.
Unbilled time is real money you've earned. The WIP ageing report is how you stop letting it slip through the gap between doing the work and getting paid for it.