The verdict in three sentences
A London accounting firm that wants to centralise client files, tax deadlines, DMS and billing chooses between a vertical solution at GBP 25-80 per user per month and a custom module of GBP 22,000-45,000 wired onto the existing stack. The vertical wins on fast start-up and built-in regulatory updates; custom wins the moment your processes are atypical or headcount passes 12-15. The real gain is not the software price but the 30 % of admin time reclaimed and the tax deadlines never missed.
What must the tool cover, and what does it cost?
A modern firm handles four blocks: matter tracking, the tax calendar (VAT, corporation tax, filings), the DMS (document management system) and fee billing. Here are the 2026 market orders of magnitude.
| Solution | Pricing model (2026) | Annual cost for 12 users | Included |
|---|---|---|---|
| Xero Practice Manager | GBP 25/user/mo | GBP 3,600 | Jobs, time, WIP |
| IRIS Elements | GBP 45-65/user/mo | GBP 6,480-9,360 | DMS, portal, tax |
| CCH Central (Wolters Kluwer) | GBP 60-80/user/mo | GBP 8,640-11,520 | Full production + BI |
| Custom module | GBP 22,000-45,000 one-off | ~GBP 8,000/yr over 5 years | Exact scope, code ownership |
On top of these come configuration (GBP 1,800-5,500), data migration and training. A vertical deploys in 4-8 weeks; a custom module in 10-16 weeks.
Custom build: what you actually develop
Custom only makes sense if it removes a friction the vertical cannot. It is usually layered on top of your existing production tool.
| Developed block | Range (GBP) | Measurable benefit |
|---|---|---|
| Automated tax deadline board | 5,500-11,000 | Zero missed deadline, D-15/D-3 alerts |
| DMS with indexing and full-text search | 7,000-13,500 | Document found in < 10 s |
| Client portal (upload, e-signature) | 6,500-12,500 | -40 % email back-and-forth |
| Fee billing + auto reminders | 4,500-9,000 | Collection time -18 days |
| Connectors (bank, HMRC, payroll) | 3,500-8,000 | Re-keying eliminated |
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Mini case study
Sophie, partner at a 12-person firm in London, pays GBP 8,640/yr in CCH licences but loses hours to re-keying and manual chasing. She invests GBP 28,000 in a custom module (client portal, indexed DMS, automated reminders) wired onto her production tool. Over 12 months: admin time down 30 %, roughly 0.8 FTE freed (worth ~GBP 30,000/yr loaded) and collection time cut by 18 days. The module pays for itself in under 14 months, then costs only maintenance.
FAQ
Must I drop my current vertical? Rarely. In 70 % of cases you keep the production engine (CCH, IRIS) and build a custom layer for DMS, client portal and reminders. Typical cost: GBP 22,000-36,000.
How long to deploy a custom module? Expect 10-16 weeks depending on scope, with progressive go-live. A useful MVP (portal + deadlines) can ship in 6-8 weeks.
Is custom GDPR-compliant and confidential? Yes, provided UK/EU hosting, encryption at rest and in transit, and fine-grained access rights. It is built into the spec from day one.
At what headcount does custom pay off? Generally above 12-15 staff, or earlier if your processes are highly specific. Below that, a well-configured vertical stays cheaper.
Can I recover my data if I switch vendor? With custom, you own the code and database: guaranteed export. That is a decisive edge over vertical-suite lock-in.
Let's scope your project. Tell us your current production tool, headcount and the 2-3 priority frictions: we price a layered module between GBP 22,000 and 45,000. 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.
