Most law firms are losing revenue every month, and have no figure to show for it.
The work was done. The client would have paid for it. It simply never made it into a time entry, which means it never reached an invoice, and never reached the accounts. There is no write-off line item, no flag in the billing report, just an absence where revenue should be.
That invisibility is precisely what makes the problem so persistent. A firm that invoices and then writes off a time entry has a measurable loss it can address. A firm that never records the time has no number to work with, only a vague sense that billing could be higher. The first step toward changing that is making the gap visible.
Law firm financial reports are built from what was invoiced and collected. They have no mechanism for capturing what was earned but never billed. The profit-and-loss statement, the WIP report, the billing realisation summary: each of these tells the story of work that made it into the billing system. None of them tell the story of work that did not.
This is not a failure of accounting. It is simply the nature of a record-based system. You can only measure what is in the record.
The practical consequence is that a firm can have a healthy-looking set of financial reports while consistently losing a significant proportion of its earned revenue. The partners see the invoiced figures. They do not see the gap between those figures and what was actually generated.
Understanding what that gap looks like requires a different kind of audit, one that compares what the firm did against what it billed, rather than simply reviewing what it billed.
The following approach does not require specialist software or a formal review process. It can be done with calendar exports, billing system reports, and a straightforward comparison. The goal is not precision but orientation: a meaningful estimate of where the gap sits and what is causing it.
Start with calendar attendances. Pull a single month of calendar data for two or three fee earners and identify every client-related meeting, conference, or attendance. Then pull the corresponding billing records for those matters and check whether each attendance was invoiced, at what duration, and whether the preparation beforehand and any follow-up correspondence appear in the record. In most firms, a gap becomes apparent quickly. Some attendances will be present but without associated preparation time. Others will be absent entirely.
Compare document activity against time entries. Ask a fee earner to identify the documents they worked on during a single week, whether drafting in Word, reviewing a contract, or annotating a brief. Cross-reference that list against their time entries for the same period. It is common to find that several of those work sessions do not correspond to any time entry, particularly shorter sessions that the practitioner did not consider worth recording individually.
Review write-off rates at the pre-bill stage. When a billing specialist or partner reviews time entries before issuing an invoice, entries that are vague, incomplete, or difficult to justify are often reduced or removed. The write-off rate at this stage, expressed as a percentage of total WIP reviewed, is a proxy for capture quality. A high pre-bill write-off rate typically indicates that entries are being recorded retrospectively and lack the detail needed to survive review. It does not mean the work was not done. It means the record was not good enough.
Look at after-hours activity. Review email and document activity outside standard hours for a sample period and compare against time entries logged. After-hours work is among the most consistently under-recorded category in most firms. A practitioner who reviews a document on Sunday evening and does not log it until Monday morning, if they log it at all, is illustrating a pattern that repeats across the entire firm.
Firms that go through this exercise for the first time are often surprised by the results. Not because the individual gaps are large, but because they are so consistent.
A single missed preparation session here, a short email thread not logged there, an after-hours review that fell out of the record. None of these looks significant in isolation. Across a working month, across all fee earners and all matters, the cumulative figure can be substantial.
The exercise also tends to surface where the loss is concentrated. In some firms, the gap is largest among practitioners who record time infrequently and in large blocks. In others, it sits disproportionately in certain matter types, particularly high-volume, lower-value matters where the administrative overhead of recording small increments feels disproportionate to the task. Knowing where the gap is concentrated is what makes it addressable.
These two categories are often conflated, but they represent fundamentally different problems and require different responses.
A write-off, or write-down, happens after a time entry has been recorded. The entry exists in the billing system and is then reduced or removed before the invoice is issued, either because the entry is vague, the time feels excessive, or a partner makes a judgement call about the client relationship. The work is visible, even if the revenue does not survive to the invoice.
An unbilled loss is different. It happens before the entry is ever created. The work was done, the time was spent, and nothing was recorded. There is no entry to review, no decision point to intervene at. The loss is silent.
Most firms have a clearer picture of their write-offs than their unbilled losses, precisely because write-offs leave a trace in the billing system. The unbilled category requires active investigation to quantify, which is why it tends to be underestimated even by firms that take billing seriously.
A firm that completes this kind of audit for the first time typically comes away with two things: a clearer estimate of what the gap actually costs, and a better understanding of where in the billing process the leakage is occurring.
Neither of those things is possible without looking. Firms that continue to manage billing purely through financial reports will continue to see only what was invoiced. The gap will remain, priced into the firm's operations as an invisible cost that no one has named.
Making it visible does not solve it. But it is where every meaningful improvement to billing accuracy begins.
This article is for general informational purposes only and does not constitute legal or financial advice.
