The verdict in three sentences
Turning a business application sold as annual licences into a multi-tenant subscription SaaS costs 25,000 to 60,000 EUR (about 27,000 to 65,000 USD) in 2026 with a nearshore team, for 3 to 5 months of work; a New York agency typically quotes two to three times more. Stripe Billing charges 0.7% of volume on top of card fees, which stays cheaper than an in-house billing engine up to roughly 3 million EUR of annual revenue. Migrations rarely fail on payments: they fail on data isolation between tenants and on e-invoicing compliance when you bill European customers.
What the multi-tenant budget covers
| Component | Content | Timeline | 2026 cost |
|---|---|---|---|
| Multi-tenant architecture | Schema or tenant-key isolation, subdomains | 4 to 6 weeks | 8,000 to 18,000 EUR |
| Stripe Billing integration | Plans, trials, proration, customer portal | 2 to 4 weeks | 5,000 to 10,000 EUR |
| Quotas and plan limits | Users, storage, API calls | 1 to 3 weeks | 3,000 to 8,000 EUR |
| E-invoicing | Structured formats, certified platform connector | 2 to 3 weeks | 4,000 to 9,000 EUR |
| Existing customer migration | Licence takeover, contract mapping | 2 to 4 weeks | 3,000 to 10,000 EUR |
| Vendor back office | MRR, churn, unpaid invoices tracking | 1 to 2 weeks | 2,000 to 5,000 EUR |
A vendor starting from a live single-tenant application usually lands around 35,000 to 45,000 EUR. A full data model rewrite pushes toward the top of the range.
Stripe Billing or in-house billing: the math
Stripe Billing takes 0.7% of billed volume on the pay-as-you-go plan, on top of card fees (2.9% + 0.30 USD in the US, 1.5% + 0.25 EUR for European cards). ACH and SEPA debits cost much less per transaction.
| Annual billed volume | Stripe Billing fee (0.7%) | In-house billing (estimated annual upkeep) | Most cost-effective |
|---|---|---|---|
| 200,000 EUR | 1,400 EUR | 12,000 to 18,000 EUR | Stripe Billing |
| 500,000 EUR | 3,500 EUR | 12,000 to 18,000 EUR | Stripe Billing |
| 1,000,000 EUR | 7,000 EUR | 15,000 to 20,000 EUR | Stripe Billing |
| 3,000,000 EUR | 21,000 EUR | 18,000 to 25,000 EUR | Worth studying |
| 6,000,000 EUR | 42,000 EUR | 20,000 to 30,000 EUR | In-house or negotiated contract |
Below 3 million EUR billed, proration, dunning and expired card logic are not worth rewriting.
E-invoicing in 2026: what changes for a SaaS vendor
Since September 1, 2026, every French company must be able to receive electronic invoices, and large and mid-size companies must issue them; SMEs follow on September 1, 2027. A B2B SaaS, even one based in New York, that bills French customers must produce structured invoices (Factur-X, UBL or CII) and send them through a certified platform.
| Requirement | What the SaaS must do | Indicative cost |
|---|---|---|
| Structured format | Generate Factur-X from Stripe invoices | Included in module (4,000 to 9,000 EUR) |
| Certified platform | API connector to the chosen platform | 0.10 to 0.40 EUR per invoice |
| Mandatory fields | Customer company ID, delivery address, nature of transaction | Configuration |
| E-reporting | Transmission of foreign customer data | Depends on volume |
| Archiving | 10-year retention with legal value | 20 to 80 EUR per month |
Mini case study
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Julien, CEO of an industrial maintenance software vendor, sells 140 annual licences at 2,400 EUR. He switches to a 220 EUR monthly subscription with a 14-day trial. Project cost: 42,000 EUR over 4 months. First-year billed volume: 140 customers x 220 EUR x 12 = 369,600 EUR, plus 30 new customers attracted by the no-commitment entry, i.e. 79,200 EUR more in a full year. Stripe Billing fees: 0.7% of 448,800 EUR = 3,142 EUR. The 30 extra customers pay back the project in just over 6 months.
FAQ
Do I need one database per customer?
Not for most vendors. Tenant-key isolation with row-level security works up to several thousand customers; a dedicated database is justified for demanding accounts, billed 150 to 400 EUR more per month.
Does Stripe handle sales tax and VAT?
Stripe Tax calculates US sales tax and European VAT for 0.5% of the relevant volume. Above roughly 200 customers across several US states, it usually pays for itself.
How long does migrating existing customers take?
Plan 4 to 8 weeks of transition with proration of current licences. In practice, 85 to 95% of customers switch if the monthly plan costs less than 115% of the old licence per month.
How do I handle failed payments?
Stripe's automatic retries usually recover 30 to 50% of failed payments. The SaaS should also include progressive suspension after 7 to 21 days.
Where should the SaaS be hosted?
US customers accept US regions, but 8 out of 10 European B2B buyers expect EU hosting for GDPR reasons. Running a second region adds 0 to 15% to hosting costs.
Let's scope your project. Tell us about your software, customer count and target pricing plans, and we will price the multi-tenant and Stripe Billing migration over 3 to 5 months. 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.
