The verdict in three sentences
For a London accounting firm, the real 2026 decision sits between a vertical SaaS (per-user subscription), a vendor licence (fixed cost plus maintenance) and a custom build (heavy upfront cost but controlled TCO). The headline price means nothing until you have costed the 3-year TCO including integrations, training and maintenance. Below 8 staff, SaaS almost always wins; above 15, custom becomes profitable.
The three pricing models head to head
The 2026 London market is structured around three billing logics. Vertical SaaS (cloud editors specialised in accounting) bills per staff member per month. The classic vendor licence requires a usage fee then annual maintenance of 18 to 22%. Custom means a one-off development cost then hosting and evolutive maintenance.
| Model | Entry cost (EUR) | Annual recurring (EUR) | Time to go live |
|---|---|---|---|
| Vertical SaaS (8 users) | 0 to 1,500 (setup) | 3,900 to 7,200 | 2 to 4 weeks |
| Vendor licence | 12,000 to 25,000 | 2,400 to 5,500 (maintenance) | 6 to 10 weeks |
| Targeted custom | 35,000 to 65,000 | 6,000 to 12,000 | 3 to 5 months |
| Hybrid (SaaS + connectors) | 4,000 to 9,000 | 5,000 to 9,000 | 4 to 8 weeks |
A firm of 8 staff on the fence should focus on the recurring line: over 3 years, EUR 5,000/year of SaaS = EUR 15,000, whereas a custom build at EUR 50,000 entry only becomes competitive with a larger headcount or a very specific business need.
What each module really costs
The classic trap: signing on a base price then discovering that the document management, client portal and bank feed are separately billed options. Here are the 2026 ballparks for the modules that come up most in London tenders.
| Module | Custom (EUR) | SaaS option (EUR/year) | Business impact |
|---|---|---|---|
| DMS + invoice recognition | 8,000 to 14,000 | 900 to 1,800 | Data entry cut by 3 |
| Secure client portal | 6,000 to 11,000 | 600 to 1,400 | Fewer emails, GDPR control |
| Bank feed (aggregation) | 4,500 to 8,000 | 480 to 1,200 | Automated reconciliation |
| E-invoicing 2026 | 5,000 to 9,000 | included at 900 | Reform compliance |
| Engagement dashboard | 5,500 to 10,000 | 600 to 1,100 | Profit per file |
The e-invoicing reform being phased in makes the compliance module non-negotiable in 2026: budget it from the start, not as a change order.
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Mini case study
Mark, partner at an 11-person accounting firm in central London, hesitates between a vertical SaaS at EUR 5,400/year and a custom build at EUR 48,000 + EUR 8,000/year. Over 3 years, SaaS costs EUR 16,200; custom EUR 72,000. But SaaS forces him to keep two side tools (portal + DMS) at EUR 2,600/year, i.e. EUR 24,000 over 3 years in total. Custom integrates everything and, by his estimate, saves 1.5 h/day/staff during tax season. At EUR 45 loaded hourly cost and 90 peak days, that is roughly EUR 67,000 of recovered time per year across the team. Custom pays back in under 18 months. Mark opts for hybrid year one, then switches.
FAQ
What is the minimum budget to start cleanly in 2026? Count at least EUR 3,900/year for a serious vertical SaaS at 8 staff, setup and training included. Below that, you get a generic tool poorly suited to accounting.
How much does team training cost? Between EUR 1,200 and 4,500 depending on headcount and model. A custom build usually needs 2 to 3 days of support, roughly EUR 3,000.
What percentage is annual maintenance? On a licence or custom build, count 18 to 22% of the initial cost per year. On a EUR 50,000 custom build, that is EUR 9,000 to 11,000/year including fixes and minor upgrades.
How fast are you operational? From 2 to 4 weeks for SaaS, 3 to 5 months for a full custom build. Historical data migration is what stretches timelines the most.
Is custom profitable for a small firm? Rarely below 10 staff. The 2026 tipping point sits around 12 to 15 users, where saved time and side subscriptions exceed the upfront investment.
Let's scope your project. Tell us your headcount, priority modules and indicative budget, and we will cost the most profitable model for your firm. 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.
