Every law firm partner faces a fundamental choice: charge by the hour or agree a fixed fee for the work. The decision affects not just client relationships but also your firm's cashflow, profit recognition, and VAT obligations.

This article compares fixed fee and hourly billing models for UK law firms. We look at the tax and accounting implications, the practical differences for solicitors, and how each model affects your firm's financial health. Whether you run a high-street conveyancing practice or a City litigation department, understanding the trade-offs matters.

How Each Billing Model Works

Hourly Billing

Under hourly billing, the solicitor records time spent on a matter and invoices the client at an agreed rate. The client pays for the actual time incurred. This model is common in litigation, corporate work, and complex advisory matters where the scope is uncertain.

From an accounting perspective, revenue is recognised as the work is performed, provided the firm can reliably measure the time and the client has accepted the basis of charging. Under FRS 102, law firms typically recognise revenue on an earnings basis, meaning work-in-progress (WIP) is valued at the billing rate for unbilled time.

Fixed Fee Billing

With a fixed fee, the solicitor agrees a single price for a defined piece of work. The client pays that amount regardless of how much time the solicitor spends. Fixed fees are standard in conveyancing, probate, and volume personal injury work.

Revenue recognition for fixed fees follows the same earnings basis under FRS 102. The firm recognises revenue proportionally as the work is completed. If the fee is paid in advance, the firm holds the money as deferred income (a liability on the balance sheet) until the work is done.

VAT Timing: A Critical Difference for Solicitors

VAT timing is one of the most practical differences between the two billing models. Under VAT rules, a solicitor must account for VAT at the earliest of: the date a VAT invoice is issued, the date payment is received, or the date the service is performed (the "basic tax point").

For hourly billing, the solicitor typically issues an invoice after the work is done. The VAT point is the invoice date. The firm pays the VAT to HMRC on its next quarterly return. Cashflow is straightforward: the client pays the invoice, and the firm remits the VAT.

For fixed fees, the position can be more complex. If the client pays the fixed fee in advance (common in conveyancing), the solicitor receives the money before the work is performed. The VAT point is the date of receipt, not the date the work is done. The firm must account for VAT on the full amount received, even though the work may not be complete for weeks or months.

This creates a cashflow mismatch. The firm receives the fee, pays the VAT to HMRC, and then incurs the costs of doing the work. If the fixed fee is too low, the firm can end up paying VAT on a loss-making matter. Solicitors who use fixed fees must price carefully and consider staging payments to align VAT receipts with work progress.

Profit Recognition and WIP

The billing model directly affects how profit is reported in the firm's accounts. Under hourly billing, the firm builds up WIP as time is recorded. At the year end, the WIP is valued and included in turnover. This means profit is recognised as the work is done, not when the invoice is paid.

Under fixed fees, the firm recognises profit proportionally. If a conveyancing matter is 60% complete at the year end, 60% of the fixed fee is recognised as revenue. The remaining 40% sits as deferred income. This can smooth profit recognition but requires careful tracking of completion stages.

For partnership and LLP structures, the timing of profit recognition matters for partner tax. Partners are taxed on their share of the firm's accounting profit for the year, not on cash drawings. If the firm uses fixed fees and recognises revenue on a staged basis, partners may pay tax on profit before the cash is actually received. This is a common issue for conveyancing firms with long pipelines of fixed-fee work.

Cashflow Implications for Law Firms

Hourly billing generally produces more predictable cashflow. The solicitor does the work, issues the invoice, and the client pays. There is no advance payment and no deferred income. The firm's cash position closely tracks its work in progress.

Fixed fee billing can create cashflow volatility. If the firm receives large advance payments, it has cash in the bank but must hold it as deferred income. The cash is not "free" it is owed to HMRC for VAT and to the client for uncompleted work. Firms that rely heavily on fixed fees need robust cashflow forecasting to avoid spending money that belongs to HMRC.

A common mistake among solicitors is treating advance fixed fees as available profit. The money is not profit until the work is done. Partners who draw against advance fees risk personal tax bills on income that has not yet been earned.

Which Model Suits Your Practice?

The right billing model depends on the type of work your firm does and your client base.

  • Litigation and corporate work typically suits hourly billing. The scope is uncertain, and clients expect to pay for actual time. Hourly billing also aligns with the firm's cost base: if a matter takes longer than expected, the firm is compensated.
  • Conveyancing and probate work well with fixed fees. Clients want certainty on cost, and the work is relatively standardised. Fixed fees also reduce the administrative burden of time recording.
  • Mixed practices often use both models. A firm might charge fixed fees for standard transactions and hourly rates for complex or contentious matters. This hybrid approach gives clients choice and spreads the financial risks across both models.

Whichever model you choose, the key is to understand the tax and accounting consequences. Fixed fees require careful VAT planning and profit recognition. Hourly billing demands disciplined time recording and WIP valuation.

Practical Tips for Solicitors

If you are considering changing your billing model, start with a review of your current fee structure. Look at your average matter duration, typical payment terms, and VAT return dates. A simple spreadsheet model can show you the cashflow impact of switching from hourly to fixed fees or vice versa.

For firms using fixed fees, consider staging your invoices. Instead of taking the full fee upfront, invoice in tranches as key milestones are reached. This aligns VAT receipts with work progress and reduces the deferred income balance on your balance sheet.

For firms using hourly billing, review your WIP valuation method. Under FRS 102, you must value WIP at the lower of cost and net realisable value. Many firms undervalue WIP, which understates profit and can lead to tax surprises for partners.

Finally, talk to your accountant about the specific implications for your firm. A legal-sector specialist can model the tax and cashflow effects of each billing model and help you choose the structure that fits your practice.

Conclusion

Fixed fee and hourly billing are both valid models for UK law firms. The right choice depends on your practice area, client expectations, and financial management capabilities. Hourly billing offers predictability and aligns revenue with effort. Fixed fees give clients certainty and can reduce administrative costs.

But both models have tax and accounting consequences that solicitors must understand. VAT timing, profit recognition, and cashflow management are not optional considerations. They affect your firm's profitability and your partners' personal tax positions.

If you are unsure which model suits your practice, speak to a legal-sector-specialist accountant. They can review your current billing structure, model the financial impact of a change, and help you implement a fee structure that works for your firm and your clients.

For more guidance on law firm accounting, see our services page and solicitor guides.