The verdict in three sentences
IRIS and CCH dominate the UK market but bill 35 to 70 GBP/user/month (Cegid/ACD 55-95 EUR in France), a cost that rises with every hire and every annual increase. Custom software costs 60,000 to 130,000 EUR upfront plus 15% annual maintenance, but freezes your bill and makes you the owner of data and workflows. Custom becomes worthwhile from 30 seats and a 4-6 year horizon, especially if your review processes or payroll integration fall outside vendor standards.
2026 suite comparison
Vertical suites include regulatory compliance (filing, VAT, audit trail) but impose their ergonomics and sometimes per-file or per-return fees.
| Criterion | Cegid / ACD | IRIS / CCH | Custom |
|---|---|---|---|
| Price /user/month | 55-95 EUR | 35-70 GBP | 0 |
| Upfront cost | 2,000-6,000 EUR | 1,500-5,000 GBP | 60,000-130,000 EUR |
| Fee per return | 0-5 EUR | variable | 0 |
| Filing compliance | included | included | to maintain (maint.) |
| Custom workflows | limited | limited | full |
| Data ownership | vendor | vendor | firm |
| Payroll/billing integration | connectors | connectors | native custom |
Five-year TCO for 30 seats
At 75 EUR/user/month, 30 seats mean 27,000 EUR/year. Over 5 years with 4%/year increases, you exceed 145,000 EUR. That is the number to put against custom.
| Scenario, 30 seats | Upfront | 5-year total |
|---|---|---|
| IRIS/CCH 75 EUR/month | 4,000 EUR | 150,000 EUR |
| IRIS/CCH 95 EUR/month | 6,000 EUR | 190,000 EUR |
| Custom 90,000 EUR + 15% | 90,000 EUR | 157,500 EUR |
| Custom 70,000 EUR + 15% | 70,000 EUR | 122,500 EUR |
At 30 seats, custom at 70,000 EUR is already cheaper than the suite from year 4, and the gap widens with every hire.
The real tipping points
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Price is not the only argument. You switch to custom when: your review workflows are non-standard, you want native payroll/billing integration, you require full data ownership, or you want to remove per-file fees that balloon with your client base.
Mini case study
Claire, finance director at a 30-staff London firm, pays IRIS 82 EUR-equivalent/user/month, or 29,520 EUR/year. Over 5 years with increases: about 165,000 EUR. A custom vendor quotes 88,000 EUR + 15% maintenance, or 154,000 EUR over 5 years. The 11,000 EUR gap is modest, but custom removes 6,000 EUR/year of per-file fees and gives her a review engine tailored to her audit work, an unpriced but decisive gain.
FAQ
At how many seats does custom pay off? Around 30 seats with a 4-6 year horizon. Below 20 seats, IRIS, CCH, Cegid or ACD remain cheaper.
Can custom keep tax filing compliant? Yes, but it requires 15%/year maintenance to track annual regulatory changes. That is the price of independence.
How much does migration from IRIS cost? Expect 5,000-15,000 EUR via standard export and API, depending on file volume and historical data to import.
Does custom handle payroll integration? Yes, it is one of its strengths: a native integration with your payroll or billing tool, with no third-party connector to maintain.
How long for a full custom tool? Expect 5 to 9 months for a production + review + filing core, delivered in batches so your business is never blocked.
Let's scope your project. Firm of 25 to 50 seats looking to leave IRIS, CCH, Cegid or ACD, indicative budget 60,000-130,000 EUR + maintenance. 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.
