The verdict in three sentences
A SaaS application in production costs 15 to 25 % of its initial build budget every year in corrective, evolutive and security maintenance, excluding hosting. For a SaaS with 300 customers, that usually means a retainer of 8 to 20 days a month at EUR 650 to 900 per day in the Amsterdam market, plus EUR 400 to 2,000 of monthly hosting. The trap is not overspending, it is underbudgeting: a V1 without planned maintenance piles up technical debt that doubles the cost of new features within 18 months.
What SaaS maintenance actually covers
The founder of a field service SaaS for landscaping contractors, launched in Amsterdam a year ago, usually discovers after V1 that the work has only just begun. Application maintenance splits into four families:
- Corrective: customer-reported bugs, regressions, incompatibilities with a new browser or mobile OS release.
- Security: monthly dependency updates, vulnerability patches, certificate renewals, access reviews.
- Evolutive: features customers ask for, such as quoting, e-signature or an offline mobile app for field crews.
- Adaptive: legal and partner changes, for instance EU e-invoicing under the ViDA package, the NIS2 duties of your larger customers, or a payment provider's new API.
| Maintenance type | Share of annual budget | Examples for a field service SaaS |
|---|---|---|
| Corrective | 20 to 30 % | Timesheet calculation bug, broken PDF export |
| Security | 10 to 15 % | Monthly updates, yearly access audit |
| Evolutive | 45 to 60 % | Quoting module, offline mobile planning |
| Adaptive | 5 to 15 % | E-invoicing, new banking API |
| Level 2 support | 5 to 10 % | Analysis of tickets escalated by customer support |
Three contract models and their price
The Dutch market offers three formulas. Day rates below are 2026 orders of magnitude for a team of experienced developers in the Randstad.
| Model (2026 order of magnitude) | Volume | Monthly cost | Annual cost |
|---|---|---|---|
| Light retainer | 8 days a month at EUR 650 | EUR 5,200 excl. VAT | EUR 62,400 excl. VAT |
| Standard retainer | 12 days a month at EUR 750 | EUR 9,000 excl. VAT | EUR 108,000 excl. VAT |
| Intensive retainer | 20 days a month at EUR 900 | EUR 18,000 excl. VAT | EUR 216,000 excl. VAT |
| Time and materials | As needed, at EUR 850 a day | Variable | Often 20 % dearer for the same volume |
| Cloud hosting | 300 active customers | EUR 400 to 2,000 | EUR 4,800 to 24,000 |
A retainer beats time and materials on two counts: it secures the team that knows the code, and it enforces a steady release rhythm. Time and materials only suits stable products that change little.
The SLA: what the contract must say
A maintenance contract without response commitments is a vague promise. For B2B SaaS, four clauses are essential:
| Incident level | Definition | Response time | Fix time |
|---|---|---|---|
| Critical | Service down or data loss | 30 minutes | Within 4 h |
| Major | Key feature degraded for all customers | 2 h | Within 1 business day |
| Minor | Annoyance with a workaround | 1 business day | Next release |
| Change request | New requirement | Estimate within 5 days | Per quarterly roadmap |
Add ownership of code and infrastructure in your name, up-to-date documentation and a reversibility clause requiring the provider to hand over the project within 30 days if you switch teams.
Mini case study
Lotte de Vries founded a field service SaaS for landscaping contractors in Amsterdam. V1 cost EUR 300,000. She has 300 customers at EUR 99 a month, or EUR 356,400 of annual recurring revenue.
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She picks a retainer of 8 days a month at EUR 700, or EUR 67,200 a year, which is 22.4 % of the V1 cost. Hosting runs at EUR 900 a month, or EUR 10,800 a year. Her total maintenance budget reaches EUR 78,000, about 22 % of revenue.
Of the 96 annual days, 24 go to fixes, 12 to security and 60 to features. The quoting module shipped in Q2 allowed a price move to EUR 109, worth EUR 36,000 of extra revenue a year on the same customer base. Evolutive maintenance pays for more than half of itself in year one.
FAQ
Why 15 to 25 % and not less?
Below 15 %, security updates and fixes absorb the whole budget and the product stops moving. Above 25 %, it often signals a fragile V1 that needs stabilising before adding features.
Should we keep the V1 team?
Preferably for at least 12 months. Switching teams usually costs 15 to 25 days of handover and code audit before the first useful fix.
How can we cut the hosting bill?
Measure first. On a 300-customer SaaS, an audit of instances, databases and backups often trims the bill by 20 to 35 % with no performance loss.
What should a monthly security update cover?
Code dependencies, server operating systems, a review of admin accounts and a backup restore test. Plan 1 to 2 days a month for an application of this size.
How does this compare with maintaining a brochure website?
It is far cheaper, since there is no business logic or customer data. Kolonell's website maintenance runs from 53 to 183 EUR a month, while SaaS maintenance is quoted on the number of days required.
See also the apprenticeship tracking web app in Dublin and our custom web app and SaaS service.
Let's scope your project. We audit your application and propose a maintenance retainer with a written SLA, up and running within 2 weeks. 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.
