The verdict in three sentences
An accounting practice with 40 to 60 staff does not need to replace its production software, it needs a custom layer that ties together engagement letters, time tracking and billing. In 2026 this kind of project costs EUR 35,000 to 70,000 (roughly GBP 30,000 to 60,000) in London and ships in 4 to 5 months. The payback is measured in hours freed (around 3 hours per person per week) and in loss-making engagements finally made visible.
Six tools, no view of profitability
The typical setup of a 45-person London practice: an accounts production package, an engagement letter tool, a timesheet spreadsheet, a billing system, a document management system and client email. Each tool works, but none of them talk to each other. The result: the partner discovers at year end that an engagement billed EUR 4,800 consumed 92 hours.
| Task | Time lost per person per week | Main cause |
|---|---|---|
| Re-keying timesheets | 45 min | Spreadsheet separate from production |
| Preparing invoices | 40 min | Manual matching of time and engagement letters |
| Searching for client documents | 35 min | DMS not linked to engagements |
| Chasing missing records | 30 min | Manual emails |
| Partner reporting | 30 min | Weekly Excel exports |
| Total | 3 h | 2026 order-of-magnitude estimate |
Across 45 staff, 3 hours a week means 135 hours every week, almost four full-time equivalents absorbed by coordination.
What a custom layer includes, and what it costs
The right architecture keeps the production software in place (it handles accounts, filings and tax returns) and adds a business layer connected through an API or scheduled imports.
| Module | Function | Indicative 2026 budget (EUR, excl. VAT) |
|---|---|---|
| Production software connector | Syncs clients, engagements, deadlines | 6,000 - 12,000 |
| Engagement letters | Generation, e-signature, agreed fees | 5,000 - 9,000 |
| Time tracking | Mobile and web entry, allocation per engagement | 5,000 - 10,000 |
| Engagement profitability | Actual time vs fees, overrun alerts | 7,000 - 14,000 |
| Client portal | Document upload, automatic reminders | 6,000 - 13,000 |
| Partner dashboards | Margin per client, per staff member, per engagement | 6,000 - 12,000 |
| Total | Depending on scope | 35,000 - 70,000 |
Add UK or EU hosting (EUR 150 to 400 per month) and ongoing maintenance at 12 to 18 % of the initial budget per year. UK GDPR and professional confidentiality require fine-grained access rights and an audit log of every access.
Custom or off-the-shelf: an honest comparison
| Criterion | Off-the-shelf practice suite | Custom layer |
|---|---|---|
| Upfront cost | EUR 0 - 10,000 | EUR 35,000 - 70,000 |
| Recurring cost for 45 users | EUR 40 - 90 per user per month | EUR 150 - 400 per month hosting |
| Production software migration | Often required | None |
| Fit with the practice's processes | Limited to configuration | Complete |
| Time to go live | 2 - 6 months of migration | 4 - 5 months of development |
| Ownership of code and data | Vendor | Practice |
For 45 users at EUR 65 per month, a suite costs about EUR 35,000 over three years, before migration. Custom makes sense when the practice wants to keep its production software and steer profitability its own way.
Mini case study
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Claire, partner at a 45-person accounting practice in London, commissions a custom layer for EUR 52,000, delivered in 4.5 months. Measured gain after six months: 2.5 hours per person per week, or 112 hours weekly. At an average internal cost of EUR 45 per hour over 44 working weeks, the value freed reaches EUR 221,760 per year. Even if only a quarter of that time is redirected to billable work, the practice recovers more than EUR 55,000 in year one. The profitability dashboard also exposes 11 under-billed engagements, renegotiated at +18 % fees.
FAQ
Do we need to change our accounts production software?
No. The layer connects to the existing tool through an API or scheduled imports. The practice avoids a migration that often takes 2 to 6 months and disrupts a tax season.
How long does the project take?
Allow 4 to 5 months: 3 weeks of scoping, 3 months of development in increments, then 3 to 4 weeks of acceptance testing and training. A first module, time tracking, can be live by month two.
How is client data protected?
UK or EU hosting, encryption at rest and in transit, role-based access and an access log. These requirements represent about 10 % of the budget and are non-negotiable for a practice.
What is the annual cost after delivery?
Budget 12 to 18 % of the initial cost per year for maintenance and enhancements, so EUR 6,000 to 9,500 for a EUR 52,000 project, plus hosting.
How fast does it pay back?
Most practices recover the investment in 12 to 18 months on the hours saved alone, before counting the fee uplift from repriced engagements.
Let's scope your project. We scope your custom layer (priority modules, connectors, EUR 35,000 to 70,000 budget, delivery in 4 to 5 months) around the tools you already use. 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.
