The verdict in three sentences
A 45-person firm that runs its engagement letters, time budgets and audit files on four separate tools only sees overruns at billing time, when it is too late to act. A custom module at EUR 25,000 to 55,000 excl. VAT links the signed engagement letter to the budget, the recorded time and the work programme, and cuts overruns by about 12 %. Against a subscription of EUR 60 to 120 per user per month, custom software pays off by year three if the firm keeps its core accounting production software and only replaces the management layer.
Four tools, zero view of the engagement budget
The pattern is common in London firms of 30 to 60 people: the engagement letter is drafted in Word from a professional body template, the time budget lives in a spreadsheet, time is recorded in the practice software, and the audit follows a work programme in another tool. The result: in April the partner discovers that a file budgeted at 38 hours has consumed 52, with no signed variation.
| Step | Current tool | Observed problem | What the custom module does |
|---|---|---|---|
| Engagement letter | Word + professional body template | Multiple versions, fees not linked to budget | Generated from the client record, e-signature |
| Time budget | Shared spreadsheet | Updated once a year | Budget per cycle (purchases, sales, payroll, VAT) from the letter |
| Time recording | Practice software | No budget alert | Alert at 80 % and 100 % of budget per cycle |
| Audit | Separate audit tool | Programme not linked to hours | Working papers attached to the budgeted cycle |
| Variation | Email + Word | Rarely issued | Pre-filled variation once overrun exceeds 15 % |
| Billing | Practice software | Gap found at the end of the job | Budget vs actual vs billed, continuously |
What each option costs in 2026
Market software for accounting firms (production suites, audit tools, engagement letter platforms) is billed per user. For 45 staff the bill climbs fast, especially when two or three subscriptions are stacked.
| Option | Upfront cost | Annual cost (45 users) | 5-year cost (2026 order of magnitude) |
|---|---|---|---|
| Full vendor suite at EUR 120/user/month | EUR 8,000 (setup) | EUR 64,800 | EUR 332,000 |
| Vendor management tool at EUR 60/user/month | EUR 4,000 | EUR 32,400 | EUR 166,000 |
| Simple custom module (letters + budgets + alerts) | EUR 25,000 excl. VAT | EUR 4,500 (maintenance, hosting) | EUR 47,500 |
| Full custom module (+ audit, variations, partner dashboard) | EUR 55,000 excl. VAT | EUR 8,000 | EUR 95,000 |
| Status quo (4 tools) | 0 | Hidden cost of overruns | 12 % of fees never billed |
Custom software does not replace your accounting production software or tax filing tools: it plugs into them via API or time imports, and handles what vendors do poorly, namely the link between what was sold and what is consumed.
Timeline and scope of a typical project
| Work package | Content | Duration | Indicative budget |
|---|---|---|---|
| Scoping | Workshops with 2 partners and 3 managers | 2 weeks | EUR 3,000 excl. VAT |
| Engagement letters | Templates per engagement type, e-signature | 4 weeks | EUR 8,000 excl. VAT |
| Budgets and alerts | Budget per cycle, time import, alerts | 4 weeks | EUR 9,000 excl. VAT |
| Audit | Work programmes, attached working papers | 5 weeks | EUR 14,000 excl. VAT |
| Partner dashboard | Profitability per file, per staff member | 3 weeks | EUR 8,000 excl. VAT |
| Testing and training | Pilot on 40 files | 3 weeks | EUR 5,000 excl. VAT |
A first scope (letters, budgets, alerts) can be live in 10 weeks, before tax season.
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Claire, partner at a 45-person accounting firm in London, bills EUR 4.2 million in fees a year. The firm estimates unbilled overruns at 6 % of revenue, i.e. EUR 252,000. With a full module at EUR 55,000 excl. VAT and EUR 8,000 annual maintenance, a 12 % reduction in those overruns recovers EUR 30,240 a year, plus EUR 32,400 of subscription avoided compared with the EUR 60 vendor tool. The annual gain is about EUR 62,600, for a payback of just over 12 months.
FAQ
Do we have to drop our accounting production software?
No. The module connects to your existing software to pull time and client data. In 80 % of projects, only the engagement letter, budget and management layer is built.
Do engagement letters stay compliant with professional body standards?
Yes, templates are reproduced as-is and then configured per engagement type. The firm keeps control of the wording, and every signed version is archived with a timestamp.
How long does it take to train 45 staff?
Allow 2 hours for staff and half a day for managers. The pilot on 40 files lets us fix screens before full rollout.
Where is client data hosted?
In the UK or the European Union, GDPR-compliant, with daily backups. Hosting is included in the EUR 4,500 to 8,000 annual budget.
Can we start small?
Yes, a first package at EUR 25,000 excl. VAT covers engagement letters, budgets and alerts. Audit and the partner dashboard are added later without a rebuild.
Let's scope your project. Send us your list of tools, headcount and engagement types: we will price a first package between EUR 25,000 and 55,000 excl. VAT, delivered in 10 to 20 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.
