Published by
Throne of Profit EditorialReviewed by
William Hassell
Founder & Chief Editor, Throne of Profit
Every hour a lawyer works but hasn't billed is money the firm has already earned and hasn't yet asked for. That unbilled work — the work-in-progress sitting in the system — feels like an asset. It usually gets treated like one. But WIP has a quiet problem: the older it gets, the less of it you actually collect. A client who questions a bill for work done last week is having a conversation. A client questioning a bill for work done four months ago is having an argument.
The lag between doing the work and sending the bill is the single biggest controllable leak in most law firms' cash flow. Close that gap and unbilled time turns into money in the bank. Leave it open and a real share of your earned revenue quietly ages into a write-down.
THE WIP AGING PROBLEM
work done ──▶ time entered ──▶ bill drafted ──▶ bill sent ──▶ paid
│ │ │
fresh (0-30d) ▇▇▇▇▇▇▇▇ high recovery, few disputes
aging (30-60d) ▇▇▇▇▇░░░ memory fades, questions rise
stale (60d+) ▇▇░░░░░░ discounts, write-offs, argumentsOwner symptoms
Hours get worked but sit for weeks before they're entered, reviewed, or billed.
Bills go out in an end-of-month rush, and some matters slip to next month — again.
When old WIP finally bills, you write down a chunk of it just to get it paid.
Why this happens
Billing is nobody's favorite task, so it's the first thing that slides when the practice gets busy. Lawyers are measured on the work, not on the paperwork that turns work into revenue, so time entry and bill review drift to the bottom of the list. The firm runs on a monthly billing cycle, which means any hour worked on the 2nd waits nearly a month before it's even drafted. And because WIP looks like a stable number on a report, aging feels invisible until a client disputes a bill they barely remember — by which point the work is cold and the leverage is gone.
Common mistakes
Batching all billing to month-end, so fresh work waits weeks before it's drafted.
Letting time entry lag, so hours are reconstructed later from memory and detail is lost.
No aging visibility, so stale WIP hides inside a healthy-looking total.
Treating bill review as optional, so drafts pile up waiting on a partner's sign-off.
Never touching old WIP until it's so cold it can only be discounted or written off.
Business consequences
Slow-moving WIP costs a firm twice. First on recovery: the older a bill, the more a client questions it, the more you concede to get paid, and the more simply gets written off. Second on cash: work done in January that bills in April is three months of the firm's money financing the client's convenience for free. The firm that bills close to the work realizes more of what it earned, collects it sooner, and spends far less time arguing about invoices. The firm that lets WIP age is effectively lending money to clients — then discounting the loan. Same lawyers, same hours, materially different revenue.
How experienced operators think about it
They treat WIP as perishable, not as an asset that keeps. The mental model is speed: the shortest possible path from work done to bill sent, because value decays with every week it waits. That reframes billing from a monthly administrative chore into an ongoing operational discipline. They watch the age of unbilled work, not just the total — a firm can have healthy WIP and still be quietly bleeding recovery if too much of it is old. And they build the habit into the workflow so it doesn't depend on any one lawyer remembering: enter time daily, review bills continuously, and get invoices out while the client still remembers the value clearly.
Practical actions
Enter time daily, not weekly. Fresh entries are accurate, detailed, and defensible; reconstructed ones lose both detail and dollars.
Shorten the billing cycle. Draft and send bills more often than once a month so no hour waits weeks to be invoiced.
Watch WIP by age, not just amount. Track how much unbilled work is over 30, 60, and 90 days old, and treat rising age as the warning it is.
Move bill review out of the bottleneck. Set a standing review rhythm so drafts don't sit waiting on a partner's spare hour.
Attack old WIP first. Bill or resolve the oldest unbilled work now, before it ages into a write-off.
This is general business information, not legal or professional advice. Consult a qualified professional for your situation.
Questions every owner should ask
How many days, on average, pass between work being done and the bill going out?
How much of our unbilled WIP is more than 60 days old right now?
When old work finally bills, how much do we routinely write down to get it paid?
Frequently asked questions
Isn't unbilled WIP still an asset — why worry about how old it is?
Because WIP isn't worth its face value; it's worth what you'll actually collect, and that number falls as the work ages. A client questions a recent bill and you have a clear conversation about value they still remember. A client questioning a months-old bill barely recalls the work, so you concede, discount, or write it off to close it out. The total on the report stays flat while the collectible value inside it quietly erodes — which is why age matters more than amount.
We bill monthly and it works fine — why change the cycle?
A monthly cycle means the hour you worked early in the month waits almost four weeks before it's even drafted, then more time to review, send, and collect. That built-in lag is exactly what lets WIP age. Billing more frequently doesn't mean more work overall — it means the same work moves through the pipeline faster, bills while it's fresh, and gets disputed less. Shortening the cycle is one of the cleanest ways to lift recovery without raising a single rate.
Related articles
Running a Profitable Law Firm — the pillar.
Writing Invoice Descriptions Clients Will Actually Pay — bills that survive scrutiny.
Turning Initial Consultations Into Signed Clients — filling the top of the pipeline.
Why Jobs Take Longer Than You Quoted — the general time-leak problem.
Where Time Leaks on a Typical Job — spotting where the hours go.
Every business has more decisions than time
Whether you need help solving one problem, evaluating a major opportunity, or making a company-changing decision, Throne of Profit gives you consulting capacity on demand.
Purchase only the consulting capacity you need and use it across Weekly Focus, Strategic Focus, Financial Focus, and ThinkTank engagements.