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Custom vs vertical software for an accounting firm (2026)

Mohamed Bah·Fondateur, Kolonell
September 4, 2026
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Custom vs vertical software for an accounting firm (2026)

Custom vs vertical software for an accounting firm (2026)

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The verdict in three sentences

The vertical solution gets you live fast at low risk, but leaves you dependent on the vendor for pricing, roadmap and your data. Custom costs more upfront (30,000 to 80,000 EUR excl. VAT) but becomes an asset you own, with no per-seat cost and shaped exactly to your workflows. The decision is settled on 3-year TCO, the criticality of your differentiation, and your ability to fund an upfront investment.

2026 decision matrix

Before comparing prices, compare what each model gains or costs you.

CriterionVertical solutionCustom
Upfront cost0-6,000 EUR setup30,000-80,000 EUR
Recurring cost40-120 EUR/user/mo15-20 %/yr maintenance
Time to go live2-8 weeks3-5 months
CustomisationLimited to optionsTotal
Vendor lock-inHighLow
Code ownershipNoYes
ScalabilityVendor roadmapYour pace

Vendor lock-in is not just a word: a 15 % price rise on a 100 EUR subscription for 15 seats is 2,700 EUR/year more, non-negotiable.

The 3-year TCO, quantified

Take a 15-person firm and compare three realistic 2026 scenarios.

ScenarioDetail3-year TCO (EUR)
Vertical at 60 EUR/seat15 × 60 × 3632,400
Vertical at 100 EUR/seat15 × 100 × 3654,000
Custom 50,000 + 18 %50,000 + 2 × 9,00068,000
Custom 40,000 + 15 %40,000 + 2 × 6,00052,000

At 60 EUR a seat, vertical is unbeatable; at 100 EUR, a well-scoped custom build at 40,000 EUR is level while removing lock-in and the marginal cost of new hires.

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Mini case study

Sophie, managing partner of a 15-person firm in Lyon, pays 95 EUR/seat to a vertical vendor: 17,100 EUR/year and 51,300 EUR over 3 years. She plans to hire 5 more staff, pushing the bill to 22,800 EUR/year. A custom build at 45,000 EUR excl. VAT with 15 % maintenance works out to about 58,500 EUR over 3 years, but with no extra cost for the 5 new seats and with her own collaborative portal. Given her growth, Sophie picks custom: break-even lands in year 4, and she secures her data against a vendor that has already raised prices twice in three years.

FAQ

When does custom beat a vertical? The 2026 order of magnitude: once the per-seat price exceeds 90 EUR or your headcount grows fast, because custom has no marginal per-user cost.

What does vendor lock-in mean? The risk of enduring price hikes, a discontinued module, a roadmap that ignores your needs, and difficult data reversibility. It is a strategic risk, not just a financial one.

Can a vertical last a long time? Yes for a firm with standard processes and no software differentiation. Vertical stays the rational choice until you have a business need outside the box.

Can the two be combined? Yes: keeping a vertical for accounting production and building a custom client portal or reporting tool is a common and often optimal hybrid approach.

Do I truly own the custom code? Yes if the contract says so: source transfer, documentation and reversibility must appear in writing in the quote.

Let's scope your project. Share your headcount, current per-seat cost and growth outlook and we will model the comparative TCO. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.

Tags:#custom vs vertical#accounting firm#software choice#TCO#vendor lock-in#customisation#decision
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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.