The verdict in three sentences
An off-the-shelf suite stays the right call as long as your process fits the vendor's mould and your firm has fewer than roughly fifteen fee-earners. Custom becomes profitable when per-user billing balloons, integrations multiply, and your workflow is a competitive edge. In 2026, in London, the break-even usually sits between 15 and 25 staff over a five-year horizon.
Off-the-shelf vs custom: what you actually buy
A practice management suite (job tracking, time, billing, document management) is billed per user, per month. Fast to deploy, but you rent a standard process. Custom is an asset: you fund the build once, then only pay hosting and maintenance.
| Criterion | Off-the-shelf suite | Custom build |
|---|---|---|
| Entry cost | GBP 0-3,000 (setup) | GBP 45,000-100,000 |
| Recurring cost | GBP 40-120 / user / month | GBP 6,000-12,000 / year (hosting + maintenance) |
| Go-live time | 2-6 weeks | 12-20 weeks |
| Process fit | Medium (configuration) | Total |
| Integrations | Limited catalogue | Unlimited (custom API) |
| Ownership | None (rental) | Firm asset |
Five-year TCO: the deciding maths
Compare a 20-person firm on a suite at GBP 75 per user per month against a custom build at GBP 70,000 plus GBP 9,000 annual maintenance.
| Line item | Off-the-shelf (20 users) | Custom build |
|---|---|---|
| Year 1 | GBP 18,000 | GBP 70,000 |
| Year 2 | GBP 18,000 | GBP 9,000 |
| Year 3 | GBP 18,000 | GBP 9,000 |
| Year 4 | GBP 18,000 | GBP 9,000 |
| Year 5 | GBP 18,000 | GBP 9,000 |
| 5-year total | GBP 90,000 | GBP 106,000 |
At 20 staff, the suite is still marginally cheaper. But at 25 staff (GBP 22,500/year in subscriptions), the suite total hits GBP 112,500 over five years and overtakes custom. Add annual vendor price rises (2026 rough order: 5-8%/year) and the gap widens further.
Mini case study
Claire runs a 24-person accounting firm in London. Her current suite costs GBP 78 per user per month, or GBP 22,464/year, with a billing module that fights her annual-fee model. A custom build quoted at GBP 72,000, amortised over five years with GBP 9,000 maintenance, comes to GBP 108,000 versus GBP 112,320 for the suite (before price rises). Past break-even, custom saves about 3 hours per fee-earner per month on re-keying, roughly 860 hours/year at GBP 45: a hidden gain of GBP 38,700/year.
FAQ
Need a professional website?
Kolonell builds websites that attract clients, optimized for the Sénégalese market. Free quote in 2 minutes.
What headcount justifies switching to custom?
As a 2026 rough order, between 15 and 25 fee-earners depending on your per-user rate. Above 20 users at GBP 75/month, custom becomes competitive over five years.
What does a custom tool really cost?
Budget GBP 45,000-100,000 to build, then GBP 6,000-12,000 per year for hosting and maintenance. Scope (jobs, time, billing, document management, client portal) drives the price.
Is custom riskier than an off-the-shelf suite?
Risk is contained if you ship in functional batches and test each module. The suite's real risk is vendor lock-in and price rises you don't control.
Can custom connect to my current tools?
Yes: APIs to your accounts-production software, your document store, HMRC filing, your bank. That is precisely the edge over the suites' limited integration catalogue.
What delivery timeline should I expect?
Allow 12-20 weeks for a first usable scope, with a phased go-live by module rather than a big bang.
Let's scope your project. Send us your headcount, integrations and target scope (jobs, time, billing, document management) and we'll price buy vs build over five years. 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.
