The launch is not the finish line. Software needs hosting, security patches, bug fixes, and small changes for as long as you use it - and that ongoing cost surprises owners who only budgeted for the build. Here is what maintenance actually costs and what drives the number.
The 15-25% rule
A widely used benchmark: annual software maintenance runs 15-25% of the original development cost. Build something for €40,000 and a realistic support budget is roughly €6,000-€10,000 per year. Over a full lifecycle, maintenance often totals 2-4x the original build - which is why the cost of building is only part of the picture.
That range moves with code quality, age, and how critical the system is to your business.
What drives the number up
Three things push maintenance toward the high end:
- Technical debt. Rushed or legacy code can demand 30-40% per year - sometimes the signal it is cheaper to rebuild.
- Regulation. Compliance, audits, and security reviews add fixed overhead.
- Uptime expectations. A system needing 24/7 response costs far more than one with business-hours support.
Clean, well-tested code stays near the low end. Neglected code drifts upward every year.
What an SLA actually buys
A Service Level Agreement defines response and resolution times - not a vague promise to “fix things”. It sets priority tiers (critical outage vs minor bug), guaranteed response windows, support hours, and who pays for what. Higher guarantees cost more because they reserve people and faster escalation paths.
Match the SLA to the real cost of downtime. A booking system losing sales every minute justifies tighter terms than an internal report.
What maintenance includes
Good maintenance is not just firefighting. It covers hosting and monitoring, security and dependency updates, bug fixes, small feature changes, and backups. Bundling it into a predictable monthly retainer beats per-incident scramble - the same logic that makes automation pay off over time.
Frequently Asked Questions
Is maintenance really 15-25% every year? For most custom software, yes. Simple, well-built systems sit near 15%; complex, regulated, or aging ones climb to 25% or more.
Can I skip maintenance to save money? Only briefly. Skipped security patches, broken integrations, and accumulating bugs cost more later - often a forced rebuild instead of steady upkeep.
What is the difference between support and maintenance? Support answers problems and questions as they arise; maintenance is the proactive work - updates, monitoring, fixes - that prevents them. A good plan covers both.
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Planning support after launch?
We scope maintenance and SLAs around your real risk - predictable monthly cost, clear response times, no surprises after go-live.
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