The verdict in three sentences
For a practice with 22 staff and 650 client files, a custom engagement tracking tool costs between £16,000 and £35,000 in 2026 (about 18,000 to 40,000 EUR), roughly 2 to 3 years of a premium SaaS subscription. It pays for itself as soon as the practice recovers 5% of margin through better time recording and engagement letter control. SaaS remains the better option under 10 users, or if your processes already match market standards.
What spreadsheets really cost a 650-client practice
A shared spreadsheet looks free. In a 22-person London practice billing around £1,850,000 in fees, it still causes very concrete losses: timesheets filled in from memory at the end of the week, outdated engagement letters, VAT or Self Assessment deadlines discovered the day before, loss-making clients spotted only after year end.
| Source of loss | 2026 order of magnitude | Estimated annual impact |
|---|---|---|
| Unrecorded or underestimated time | 3 to 6% of hours | £55,000 to £110,000 |
| Out-of-scope work not billed | 1 to 2% of fees | £18,500 to £37,000 |
| HMRC penalties and surcharges on missed deadlines | 2 to 5 incidents per year | £2,500 to £10,000 |
| Manual consolidation of spreadsheets | 4 h per week for one partner | £22,000 valued |
| Loss-making clients spotted too late | 8 to 12% of the portfolio | uncorrected negative margin |
| Chasing clients for missing records | 1.5 h per day practice-wide | £16,000 valued |
The 5% margin recovery target means, on £1.85M of fees, roughly £92,500 a year. That is the figure to weigh against the cost of the tool, not the licence price alone.
Custom build or off-the-shelf SaaS: the numbers
Practice management suites handle bookkeeping and compliance well. Engagement tracking is often a side module, rigid on per-client profitability and closed to the practice's internal rules (fixed fees, budgets per cycle, allocation by partner).
| Criterion | Off-the-shelf SaaS | Custom tool |
|---|---|---|
| Upfront cost | £0 to £2,500 setup | £16,000 to £35,000 |
| Recurring cost for 22 users | £35 to £80 per user per month, i.e. £9,240 to £21,120 per year | Hosting and maintenance: £2,600 to £5,200 per year |
| Engagement letters and change orders | Standard templates | Generated from your fee scales, built-in e-signature |
| Tax and payroll deadline calendar | Generic calendar | Calculated per client by entity type, year end and VAT scheme |
| Profitability per client | Fixed report | Budget vs actual per cycle, alert at 80% of the fee |
| Link to production software | Depends on vendor | API or automated daily import |
| Time to go live | 2 to 4 weeks | 8 to 14 weeks |
Over 5 years, SaaS costs £46,200 to £105,600 for 22 users. The custom build comes to £29,000 to £61,000 all in. The gap widens as headcount grows, because custom cost does not depend on the number of seats.
The modules that drive the return
Not all modules are equal. For a practice this size, four building blocks deliver most of the gain.
| Module | Indicative budget | Expected gain |
|---|---|---|
| Time recording (web and mobile, timer) | £3,500 to £7,000 | +3% of billable hours captured |
| Engagement letters and out-of-scope tracking | £3,000 to £6,000 | 1 to 2% of fees re-billed |
| Automatic deadline calendar per client | £3,500 to £8,000 | Zero penalties, calmer filing season |
| Profitability dashboard per job and client | £4,000 to £9,000 | Loss-making fees reviewed in the first half |
| Client portal for document upload | £1,800 to £5,200 | -40% chasing |
A focused phase 1 (time, engagement letters, deadline calendar) sits around £16,000 to £19,000 and ships in 8 weeks. The client portal and advanced dashboards can follow in phase 2.
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Mini case study
Helen, partner at a 22-person accounting practice in London, bills £1.85M a year. She launches phase 1 at £21,000 plus £3,500 of annual maintenance. After six months, the practice captures 3.5% more hours out of 30,000 productive hours, i.e. 1,050 hours at an average billed rate of £68: £71,400. Add 1.2% of out-of-scope fees re-billed, i.e. £22,200. Annual gain: about £93,600 for £24,500 of first-year cost. Break-even in a little over 3 months.
FAQ
How much does custom engagement tracking software cost for an accounting practice in 2026?
For 15 to 30 staff, budget £16,000 to £35,000 (18,000 to 40,000 EUR) depending on the number of modules. Maintenance and hosting add £2,600 to £5,200 a year.
Can the tool connect to our practice management or production software?
Yes, through an API when the vendor offers one, otherwise via an automated daily import of clients and entries. This connector usually accounts for £1,800 to £4,500 of the budget.
Is client data compliant with UK GDPR and professional confidentiality?
Hosting is in the UK or the EU, with encryption, access logging and role-based permissions. A record of processing and a data protection impact assessment are delivered with the project.
From how many users does custom beat SaaS?
In practice, above 12 to 15 users, or as soon as your fee and profitability rules do not fit a SaaS. Over 5 years, the gap reaches £17,000 to £44,000 for 22 users.
How long does deployment take?
Allow 8 to 14 weeks from scoping to production, including migration of the 650 client files. Ideally, go live outside the January Self Assessment peak, between May and October.
Let's scope your project. Send us your number of clients, users and current tools for a phase 1 scoped between £16,000 and £35,000, delivered in 8 to 14 weeks. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
