The verdict in three sentences
Maintenance for a custom application costs, in 2026, between 12 and 20 % of the build cost per year, i.e. a monthly retainer of 800 to 3,500 EUR depending on the SLA. This budget covers fixes, enhancements, hosting, monitoring and quarterly security updates. Skipping maintenance saves nothing: technical debt eventually costs a full rebuild.
The maintenance grid in 2026
A director who commissioned an application must budget maintenance from delivery. The cost is driven by the chosen SLA level: the higher the guaranteed uptime and the tighter the recovery times, the higher the retainer.
| SLA level | Uptime | Recovery time | Retainer/mo |
|---|---|---|---|
| Essential | 99.0 % | < 48 business h | 800 - 1,400 EUR |
| Standard | 99.5 % | < 8 business h | 1,400 - 2,200 EUR |
| Business | 99.9 % | < 4 h | 2,200 - 3,500 EUR |
| Critical 24/7 | 99.95 % | < 1 h | on quote (> 3,500) |
The retainer usually includes a quota of corrective + evolutive hours. Beyond that, major enhancements are priced per project.
Fixes, enhancements, hosting: what maintenance covers
Maintenance blends several line items you must separate to avoid surprises.
| Line item | Nature | Indicative 2026 cost |
|---|---|---|
| Corrective tickets (bugs) | in retainer | within SLA |
| Minor enhancements | included (hour quota) | within SLA |
| Major enhancements | out of retainer | 500 - 800 EUR/day |
| Hosting + monitoring | recurring | 100 - 400 EUR/mo |
| Security updates | quarterly | included |
| Framework version upgrade | yearly | 1,500 - 5,000 EUR |
An unmaintained app accumulates technical debt: obsolete dependencies, unpatched flaws, browser incompatibilities. After 2-3 years this often forces a rebuild at 60-100 % of the initial cost.
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Mini case study
Thomas, director of a logistics SME in Lille, had a route-tracking app built for 45,000 EUR. He hesitates between "no maintenance" and a Standard retainer at 1,800 EUR/month (21,600 EUR/year, i.e. 16 % of the build). Without maintenance, a failure blocking schedules for one day costs him about 6,000 EUR in delays and customer penalties. The Standard SLA guarantees recovery within 8 hours: two incidents avoided per year cover more than half the retainer, on top of continuous security and evolvability.
FAQ
Why 12-20 % of the build per year? It is the 2026 market standard: it covers fixes, security watch, managed hosting and small enhancements. Below 12 %, maintenance is usually insufficient.
What happens if I don't maintain? The app works for a while, then accumulates flaws and incompatibilities. Technical debt turns simple fixes into a costly rebuild (60-100 % of initial cost).
Is a 99.9 % SLA worth the premium? Only if downtime is expensive (critical app, external customers, supply chain). For a non-critical internal tool, Standard is often enough.
Are enhancements included? Minor ones yes, within an hour quota. Major enhancements (new module) are priced per project, around 500-800 EUR/day.
Can we change vendor for maintenance? Yes, provided you have the source code and clean documentation. Require them in the build contract to avoid lock-in.
Let's scope your project. Tell us your application's build cost and target SLA: we propose a tailored maintenance retainer, corrective and evolutive. 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.
