The verdict in three sentences
A maintenance contract (TMA, application maintenance outsourcing) costs 12 to 22 % of development cost per year, typically 800 to 4,000 EUR/month depending on service level. It covers fixes, minor evolutions, security and support, and a 99.9 % uptime SLA with on-call adds 20 to 40 % to the price. Without maintenance, technical debt accumulates: dependencies age, vulnerabilities open, and the cost of future work climbs 30 to 60 %.
What maintenance actually covers
Maintenance is not just troubleshooting: it is an availability and security contract. Scope and SLA drive the price.
| Maintenance level | Scope | 2026 budget (EUR/month) |
|---|---|---|
| Essential | Fixes + security updates | 800-1,500 |
| Standard | + minor evolutions + 5-day support | 1,500-2,800 |
| Advanced | + 99.9 % SLA + 24/7 monitoring | 2,800-4,000 |
| Critical | + 24/7 on-call + recovery <1 h | 4,000-7,000 |
Another way to budget: apply a percentage to the initial development cost, which aligns maintenance effort with the application's size.
| Development cost | TMA at 12 %/yr | TMA at 22 %/yr | Monthly equivalent |
|---|---|---|---|
| 30,000 EUR | 3,600 EUR | 6,600 EUR | 300-550 EUR |
| 60,000 EUR | 7,200 EUR | 13,200 EUR | 600-1,100 EUR |
| 120,000 EUR | 14,400 EUR | 26,400 EUR | 1,200-2,200 EUR |
| 250,000 EUR | 30,000 EUR | 55,000 EUR | 2,500-4,580 EUR |
Why skipping maintenance costs more
An unmaintained application does not stop working overnight, but it degrades. Frameworks fall out of support, security patches stop being applied, and every evolution becomes a catch-up project.
| Consequence without maintenance | Impact at 2-3 years |
|---|---|
| Obsolete dependencies | +30-60 % on evolution cost |
| Unpatched vulnerabilities | breach / GDPR risk |
| No monitoring | outages found by customers |
| Loss of code knowledge | slow, costly dev onboarding |
| Browser compatibility | growing display bugs |
Mini case study
Sofiane is CIO of a mid-cap logistics firm in Lille running a fleet-tracking application built for 140,000 EUR. He hesitates to sign a maintenance contract. Two years unmaintained: an unpatched flaw causes an incident, two major dependencies fall out of support, and the quote for the next evolution jumps from 25,000 to 41,000 EUR (+64 %) due to technical catch-up. A Standard TMA at 2,200 EUR/month (26,400 EUR/year, ~19 % of dev cost) would have covered security, updates and minor evolutions, and avoided the 16,000 EUR overrun on that single next release.
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FAQ
What percentage of development cost should I plan for maintenance?
A rule of thumb of 12 to 22 % per year, depending on criticality, SLA and desired pace of evolution.
Does maintenance include new features?
Minor evolutions yes; large developments fall outside the retainer and are quoted separately, often at a preferential rate for maintenance clients.
What does a 99.9 % SLA guarantee?
About 8.7 hours of downtime maximum per year, with monitoring and contractual recovery times; this level adds 20 to 40 % to the base price.
Can you take over maintenance of an app built by another provider?
Yes, after a takeover audit of 2,000 to 6,000 EUR to assess code quality and secure the knowledge transfer.
What happens if I skip maintenance?
The application keeps running, but technical debt raises the cost of future work by 30 to 60 % and exposes you to uncovered security risks.
Let's scope your project. Share your application's development cost, target SLA and criticality, with an indicative budget of 800 to 4,000 EUR/month. 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.
