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Vertical SaaS vs custom for accounting firms: the numbers in 2026

Mohamed Bah·Fondateur, Kolonell
September 4, 2026
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Vertical SaaS vs custom for accounting firms: the numbers in 2026

Vertical SaaS vs custom for accounting firms: the numbers in 2026

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The verdict in three sentences

Between a vertical SaaS (fast, standard) and custom (tailored, owned), the right choice reads over 5 years, not at entry price. A SaaS at EUR 50/user/month for 15 seats costs ~EUR 45,000 over 5 years with no ownership; custom at EUR 40,000 + EUR 6,000/year maintenance comes to ~EUR 70,000 but fits your processes. The switch point depends on how specific your processes are, how many users you have, and your tolerance for vendor lock-in.

The decision matrix

Four criteria settle most cases. Here is the 2026 reading grid.

CriterionChoose vertical SaaSChoose custom
Process specificityStandard, market-closeSpecific, competitive edge
User count< 12 seats> 15 seats (heavy subscription)
Vendor dependencyAcceptableAvoid (strategic data)
Time to launchImmediate12-18 weeks acceptable
Ownership & resaleNot requiredWanted (firm asset)
Upfront budgetLow cashAble to invest

The 5-year TCO, numbers in hand

Assumption: 15 users, SaaS at EUR 50/user/month, custom at EUR 40,000 + EUR 6,000/year maintenance.

Line itemVertical SaaSCustom
Upfront costEUR 0EUR 40,000
Annual costEUR 9,000EUR 6,000
Year 1 costEUR 9,000EUR 46,000
3-year cumulativeEUR 27,000EUR 58,000
5-year cumulativeEUR 45,000EUR 70,000
7-year cumulativeEUR 63,000EUR 82,000
Code ownershipNoYes

SaaS stays cheaper cumulatively even at 7 years in this scenario. Custom is justified by non-monetary value (fit, ownership, independence) or when headcount climbs sharply: at 30 users, SaaS jumps to EUR 18,000/year and quickly catches a fixed-cost custom build.

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Mini case study

Elodie, a partner at a 22-person firm in Lyon, is torn. On SaaS at EUR 50/seat, her bill is already EUR 13,200/year, i.e. EUR 66,000 over 5 years, set to rise with hiring. Custom at EUR 45,000 + EUR 6,000/year comes to EUR 75,000 over 5 years, but the cost does not grow with headcount and the tool fits her engagement mix. At her growth pace (+3 seats/year), she tips toward custom: SaaS would exceed EUR 90,000 over 5 years.

FAQ

From how many users does custom win? As a 2026 order of magnitude, beyond 15-20 seats cumulative SaaS fees catch a fixed-cost custom build, especially under growth.

Is SaaS really risk-free? No: price increases, vendor lock-in and lack of ownership are risks to factor into the decision.

Can we start on SaaS then move to custom? Yes, a common strategy: validate needs on SaaS for 1-2 years, then build a tailored tool in-house.

How do I estimate my firm's switch point? We project your 5-year headcount, cumulative SaaS price and custom TCO: the intersection gives your switch point.

Does custom include maintenance? It is quoted separately (order of magnitude 12-15% of investment/year) covering fixes, changes and hosting.

Let's scope your project. Give us your current and projected headcount, your process specificity and budget, and we will compute your SaaS vs custom switch point. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.

Tags:#vertical SaaS vs custom#accounting firm#TCO#vendor lock-in#decision#comparison
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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.