Engagement Letter and Timesheet Software for an Accounting Firm in London

The verdict in three sentences

For a 22-person London firm, an off-the-shelf solution costs 10,500 to 23,800 EUR per year, while a custom tool requires 50,000 to 110,000 EUR upfront (excl. VAT). Custom makes sense when your engagement letters, timesheets and document collection follow a process of your own that standard software forces you to work around. Either way, the value comes from the 3 hours saved per week per staff member and from connectors to your accounting production software.

What the firm really needs to manage

An accounting firm sells time. Without reliable time tracking per client file, you cannot tell which clients are profitable, which engagement letters underestimate the real workload, or when to chase a client who has not sent their documents. The three functional blocks are linked: the engagement letter sets scope and fixed fee, timesheets measure the gap, document collection gates production.

Market solution or custom build: the 5-year numbers

Practice management software is priced in 2026 between 40 and 90 EUR per user per month. For 22 users, that is 880 to 1,980 EUR per month. Custom reverses the logic: a heavier initial investment, then maintenance of roughly 15% per year.

Custom becomes relevant above 30 staff, during acquisitions (buying firms with different processes) or if you sell atypical engagements: advisory, outsourced payroll, annual company secretarial work, which standard templates handle poorly. Below that, a well-configured market solution is often the best choice.

Watch-outs before signing

Three topics come up in every London project we see. First, data hosting: client documents contain personal and banking data, so UK or EU hosting and UK GDPR compliance are a minimum. Second, historical data migration: importing three years of timesheets allows immediate comparison. Third, adoption: a timesheet tool staff never open is worthless, and mobile entry in under 30 seconds is a decisive criterion.

Mini case study

Claire, partner at a 22-person accounting firm in London, bills an average of 85 EUR per hour. With 3 hours saved per week per staff member over 45 weeks, the firm recovers 22 × 3 × 45 = 2,970 hours per year. If only a third of that time is reallocated to billable work, that is 990 h × 85 EUR = 84,150 EUR of potential revenue per year. A custom tool at 80,000 EUR pays back in just over a year, a market solution at 16,000 EUR per year in under three months.

FAQ

How much does practice management software cost for a 20-person accounting firm?

In 2026, expect 40 to 90 EUR per user per month for a market solution, i.e. 9,600 to 21,600 EUR per year for 20 people. A custom tool starts around 50,000 EUR.

Can the tool connect to our accounting production software?

Yes, most production tools expose an API or structured exports. A custom connector usually costs 6,000 to 15,000 EUR depending on the vendor and the volume of synced data.

How long does a custom build take?

Expect 4 to 6 months for a full scope covering engagement letters, timesheets and document collection. A first usable release focused on time entry can ship in 8 to 10 weeks.

Are generated engagement letters compliant with professional body requirements?

Templates are built from the profession's standard wording and approved by your partners. Advanced e-signature, around 1 to 2 EUR per signature, gives sufficient evidential value.

How do we make sure staff log their time?

Mobile entry in under 30 seconds and automatic Friday reminders raise the time entry rate from 60% to over 90% within three months in the firms we support.

Let's scope your project. Send us your headcount, your production software and your three main pain points: we will scope the work, the indicative budget and the timeline. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.