Work in progress — the accumulated value of time and disbursements recorded on matters that have not yet been billed — is the single largest hidden asset on most law firm balance sheets. It is also, if poorly managed, one of the fastest routes to a cashflow crisis.

UK law firms collectively carry billions of pounds in WIP at any given moment. Some of that WIP is healthy: recently completed work awaiting month-end billing. Too much of it is aged, irrecoverable, or simply forgotten. According to the Law Society’s Financial Benchmarking Survey, the median firm bills and collects only around 85% of the time its fee earners record, with WIP management failures accounting for a significant share of the gap.

This guide explains what WIP is, why it accumulates, how to measure it, and — most importantly — how to reduce it systematically.

What Is WIP and Why Does It Matter?

Defining WIP in Legal Practice

In a law firm, WIP comprises two elements:

Unbilled time: hours recorded by fee earners on matters that have not yet been invoiced
Unbilled disbursements: costs paid on behalf of clients (court fees, barrister fees, search fees, expert reports) that have been incurred but not yet recharged on an invoice

WIP is distinct from debtors (invoices sent but unpaid). The billing cycle moves value from WIP to debtor to cash. A firm with high WIP and high debtors is doing a lot of work but not collecting the value it creates.

The Financial Impact

WIP has a direct cost. Every pound of unbilled time represents cash the firm has already spent — on salary, office costs, and overheads — that it has not yet recovered. At a firm with a 60% profit margin and £500,000 of WIP, roughly £200,000 of cost is sitting in unbilled matters. If that WIP takes three months to convert to cash, the firm is effectively funding a three-month interest-free loan to its clients.

For small and mid-sized firms in particular, WIP management is not a back-office administrative issue — it is a cashflow survival question. The SRA’s financial resilience assessments consistently identify WIP lock-up (the number of days’ revenue tied up in WIP) as a key indicator of firm stability.

Measuring WIP: Key Metrics

WIP Days

WIP days (sometimes called “lock-up days”) measure how many days’ worth of fee income is tied up in unbilled work:

WIP Days = (Total WIP Value / Annual Fee Income) × 365

For a firm with £1.2 million in annual fees and £200,000 in WIP, that is 61 days. Industry benchmarks vary by firm type:

High-volume commodity work (conveyancing, employment): 30–45 days is achievable
Complex litigation or corporate: 60–90 days is common; over 120 is a risk signal
Legal aid matters: often higher due to claim submission cycles

WIP Realisation Rate

The WIP realisation rate measures what percentage of recorded WIP actually converts to billed revenue:

Realisation Rate = (Amount Billed / WIP Written Off + Amount Billed) × 100

A firm billing £900,000 from £1,000,000 of WIP is realising 90%. The industry average is closer to 85%, meaning 15p in every pound of recorded time is written off at billing. Top-performing firms achieve 92–95%.

Aged WIP Analysis

Not all WIP is equal. Fresh WIP — recorded in the last 30 days — is almost always recoverable. Aged WIP — over 90 days old — has significantly lower recovery prospects. Over 180 days, much of it will never be billed.

Every firm should produce a monthly aged WIP report broken down by:

Matter
Fee earner
Age bands: 0–30, 31–60, 61–90, 91–180, over 180 days
Work type

This report is the primary management tool for WIP reduction. If it does not exist or is not reviewed regularly, WIP will silently accumulate.

Why WIP Accumulates

Time Recording Failures

The most common cause of excessive WIP is poor time recording discipline. Fee earners who reconstruct their time at the end of the week or month consistently under-record — research suggests by 15–25%. Time that is not recorded cannot be billed.

The second recording failure is inadequate narratives. A time entry that reads “telephone call — 0.3 hours” may pass the internal system but will not survive a client query or a detailed assessment. Fee earners who record vague narratives often find their billing partner writes the time off at billing rather than risk a dispute.

Billing Delays

Where billing authority sits with a senior partner who reviews all invoices before issue, a bottleneck forms. If that partner is busy, the billing run slips. WIP that should have been invoiced in October sits until November or December, and the 90-day clock starts late.

Monthly billing disciplines — where every matter is reviewed for billing at the same time each month — are far more effective than ad hoc billing.

Scope Creep Without Communication

When the scope of a matter expands but the fee earner does not update the client’s costs estimate, the fee earner becomes reluctant to bill. They know the invoice will exceed the estimate. Billing becomes uncomfortable, so it is deferred. The matter grows more WIP while the underlying communication problem is not addressed.

Legal Aid and Fixed Fee Constraint

In legal aid matters, WIP accumulates because payment is not triggered by billing time — it is triggered by completing and submitting a claim. Firms must understand the LAA’s payment cycles and billing points to manage legal aid WIP actively.

File Completion Delays

Work that is 95% complete but not formally closed is a WIP accumulation risk. Fee earners move on to new matters; the final 5% never happens; the WIP sits on the aged report indefinitely. A file closure process that requires billing sign-off before archiving is an effective structural control.

Reducing WIP: Practical Strategies

Implement a Billing Calendar

Fix a billing date each month — the last Thursday, for example — and make it inviolable. Every fee earner reviews their matter list the week before and bills everything that is billable. The practice manager produces an aged WIP report five days before the billing date so fee earners and billing partners have time to act.

Firms that move from ad hoc to calendar billing consistently reduce WIP days by 10–20 within six months.

Set Matter-Level WIP Limits

Rather than reviewing WIP only at billing, set a trigger that alerts the fee earner when WIP on a single matter exceeds a defined threshold — say, 60% of the agreed estimate or £2,000. The trigger prompts a billing review or a client communication.

This prevents any single matter becoming a WIP black hole. An alert at £2,000 is far more actionable than discovering £15,000 of aged WIP at a year-end review.

Require Contemporaneous Time Recording

The single most effective WIP reduction measure is contemporaneous time recording — logging time as it happens, not reconstructed later. The difference in accuracy is material: firms using mobile time recording tools that capture entries during or immediately after each task recover 20–25% more time than those relying on end-of-day reconstruction.

Train fee earners to record time before moving to the next task. Build it into the firm’s supervision framework: a fee earner who has not recorded any time by 11am is flagged.

Improve Narrative Quality

At billing review, the billing partner should not be making judgment calls about whether poorly narrated time entries are recoverable. If narratives are good, billing is fast and realisation is high. Invest in training; set minimum narrative standards; reject returns that do not meet them.

Bill Disbursements Promptly

Disbursements are often the most forgotten element of WIP. A £500 barrister’s fee paid six months ago and not yet recharged is cash out of pocket for the firm. Build a disbursement sweep into every billing run: before issuing the invoice, run a disbursement reconciliation report and include everything unrecovered.

Proactive Client Communication on Costs

Where a matter is running over estimate, tell the client promptly. A short email — “We wanted to update you that costs to date have reached X against our original estimate of Y. We expect the matter to conclude by [date] at a total cost of approximately Z” — is far less uncomfortable than a surprise invoice. Clients who are kept informed pay more quickly and dispute less.

WIP Management by Practice Area

Conveyancing

Conveyancing WIP should be minimal. With fixed fees and a clear completion trigger, there is no excuse for WIP older than 30 days. The risk area is abortive transactions: where a sale falls through, ensure there is a clear policy on what the client owes and invoice promptly.

Litigation

Litigation WIP is structurally higher because matters run for months or years. Manage it by setting interim billing milestones at key stages: issue, allocation, disclosure, witness statements, trial preparation. Do not wait for settlement or judgment to bill everything — by that point, much of the early WIP will be unrecoverable.

Corporate and Commercial

Transactional work carries high WIP risk on aborted deals. Build retainers or interim billing milestones into engagement letters. A deal that reaches heads of terms and then collapses should still generate a meaningful invoice — ensure your engagement letter provides for this.

Employment

For contentious employment matters, bill at each tribunal stage. For advisory retainers, monthly billing is the only sensible model.

The Technology Advantage

Modern practice management software generates real-time WIP reports and can be configured to trigger alerts automatically. Firms using such tools reduce the administrative burden of WIP reviews significantly.

AI tools are going further, automatically capturing time entries from emails and calls so that WIP reflects actual work done rather than what the fee earner remembered to record. This closes the recording gap — the difference between what was done and what was logged — which is often the largest single driver of WIP write-offs at billing.

Obiter automatically reads fee earner email and document activity to generate draft time entries, which are then presented for approval before each billing run. Firms using Obiter consistently find their aged WIP reports shrink within the first billing cycle because previously unrecorded work is surfaced before it is lost. The result is more accurate WIP, higher realisation rates, and fewer billing day write-offs.

Summary

WIP management is a discipline built on three pillars: accurate contemporaneous recording, regular billing cycles, and proactive client communication. Firms that treat WIP as a monthly management agenda item — not an annual fire-fight — convert more of the value they create into cash, run healthier balance sheets, and carry far less hidden write-off risk. The tools to do it well have never been more accessible.

Work in Progress WIP Management for Law Firms