Cut lock-up before it cuts your cash: a law firm CFO's diagnostic playbook

A law firm with strong revenue and healthy profit margins can still run out of cash. The mechanism is lock-up: the combined lag between work being done and money landing in the firm's account. At a mid-sized commercial firm billing £40 million annually, every additional day of lock-up represents roughly £110,000 in cash tied up and unavailable. Across a 100-partner firm with average lock-up of 120 days, that is over £13 million sitting in WIP schedules and aged debtor ledgers rather than in the equity partners' hands. In 2026, with base rates still elevated and credit lines more expensive than they were three years ago, the cost of carrying that float has become impossible to ignore.

The problem compounds because law firms are structurally unable to raise equity capital to buffer the gap. Partners fund the shortfall personally, through drawings retained or capital called, which makes lock-up a governance issue as much as a financial one. It also makes the diagnostic work non-negotiable.

Four steps to diagnose and cut lock-up

Step 1: split WIP days from debtor days

Lock-up is typically reported as a single combined figure (WIP days plus debtor days), which obscures where the disease actually sits. Run the two separately. WIP days measures the gap between time being recorded and a bill being raised; debtor days measures the gap between the bill being raised and cash being collected. A firm with 45 WIP days and 75 debtor days has a different problem from one sitting at 85 WIP days and 35 debtor days, even if the total is identical.

Pull this data from your practice management system at matter level, not at department level. Tools like Aderant, Elite 3E and Actionstep all carry the raw timestamps; the question is whether your finance team has built the aging reports to surface them. If you are working from department averages, you are already one analytical layer too far from the truth.

Step 2: age WIP by fee earner and matter type

Not all WIP ages equally. Contentious matters, particularly those involving litigation funding or conditional fee arrangements, will naturally carry longer WIP cycles. Transactional work, where billing milestones are tied to deal events (exchange, completion, regulatory clearance), should be tight. The diagnostic question is whether the WIP age in each category matches its structural expectation or whether it reflects billing avoidance, poor matter planning, or a fee earner who has not raised a bill in 90 days because the client conversation feels uncomfortable.

Segment the WIP schedule into four buckets: under 30 days (normal), 30 to 60 days (watch), 60 to 90 days (escalate), over 90 days (provisioning decision required). For matters over 90 days, the responsible partner should provide a written commentary. This is not punitive; it forces the firm to distinguish genuinely in-progress work from WIP that has quietly become a bad debt already priced at cost.

Reading how your firm's billing rates convert into realised revenue is the right companion analysis here, because WIP that bills at a heavy discount or writes off frequently is compounding the cash problem with a margin problem simultaneously.

Step 3: tier debtor aging for commercial clients

The debtor ledger in most law firms is managed by a credit control function that operates on a standard dunning cycle: statement at 30 days, call at 45, escalation at 60. That process is fine for volume consumer work. For commercial clients, it is insufficient.

Commercial debtors need to be tiered by relationship and analysed for dispute signals. An invoice that sits unpaid at 75 days at a corporate client is often a billing dispute in disguise: a disagreement over scope, a concern about write-ups, or a failure of the billing narrative to connect to the value the client perceives. E-billing platforms used by large corporates (eBillingHub, TyMetrix, Wolters Kluwer's Legal Spend Management suite) add another layer: an invoice rejected at validation will not even appear on the client's payment queue until the firm responds to the query. Finance teams that do not monitor rejection rates systematically will misread their debtor position.

Step 4: tie billing authority to partner accountability

The structural reason WIP accumulates is that the person who generates it (the fee earner) is not always the person who suffers the cash consequence (the equity partner or the firm). Introduce a billing authority framework where any matter with WIP over 60 days requires a partner sign-off on a billing plan, with a named target date. This is different from asking partners to bill more: it is asking them to commit to a schedule and be measured against it in their performance review.

Understanding why each matter is your real unit of financial analysis matters here, because a billing plan built at matter level will also expose whether the economics of the engagement ever made sense in the first place.

What derails a lock-up reduction programme?

The most common failure is running the lock-up exercise once, finding the culprits, and then letting the data go stale. Lock-up reporting needs to be a standing item on the monthly finance committee agenda, with trend lines rather than point-in-time snapshots.

A second failure mode is treating the trust account boundary as a cash buffer. Client money held in the firm's client account cannot be treated as a liquidity cushion; mixing that with the firm's working capitalworking capitalWorking capital is the difference between a company's current assets and current liabilities, measuring short-term liquidity and the funds available to run daily operations.View full definition → position is the kind of error that ends careers and SRA registrations simultaneously. Any lock-up reduction initiative must be run entirely on the office account side of the ledger.

The third pitfall is allowing the reduction programme to damage client relationships. Aggressive dunning on a client in the middle of a sensitive M&A process, where the firm may also be relying on the relationship for future instructions, requires judgment. The answer is not to go soft on collection but to ensure the client-facing conversation is held at partner level, not delegated to a junior credit controller.

Five lock-up quick wins to start this week

• Pull the WIP aging report for every matter over 90 days and require partner commentary by end of week
• Check your e-billing rejection rate for the top 20 corporate clients; anything above 8-10% is a billing process problem, not a client payment problem
• Identify the five fee earners with the highest average WIP days and schedule a conversation with their supervising partner before month-end
• Confirm that your lock-up metric separates WIP days and debtor days rather than reporting a blended total
• Review whether any matter with WIP over £50,000 has a documented billing plan on file

The firms that reduce lock-up durably are not the ones that run collection campaigns. They are the ones that change the billing behaviour of fee earners at the front of the matter lifecycle, before the WIP has aged into a problem. Start with the data, get it to partner level, and hold the accountability there.

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