The verdict in three sentences
A business application delivered without a support contract becomes fragile within 6 to 12 months: security updates, unfixed bugs, small changes piling up. In Amsterdam in 2026, an application maintenance retainer costs between EUR 1,500 and EUR 6,000 per month excluding VAT, with 8 to 40 hours included and a fix time of 4 to 48 hours depending on severity. Over a year, a sensible budget sits between 15 and 20% of the application's initial cost.
What a maintenance retainer covers
Application maintenance covers three kinds of work: corrective (fixing bugs), preventive (language, library and server updates, tested backups) and evolutive (small improvements requested by users). A good contract separates the three clearly, because only the first two should be guaranteed.
| Plan | Monthly price 2026 (EUR excl. VAT) | Hours included | Blocking fix time | On-call | For whom |
|---|---|---|---|---|---|
| Essential | 1,500 to 2,200 | 8 h | 24 to 48 business hours | no | internal app, under 30 users |
| Standard | 2,500 to 3,500 | 16 h | 8 business hours | business hours | invoicing or stock app |
| Enhanced | 4,000 to 5,000 | 24 to 30 h | 4 h | 7 days, 8am to 8pm | app used by customers or branches |
| Critical | 5,000 to 6,000 | 40 h | 4 h, 24/7 | 24/7 | payments, logistics |
| Out-of-scope hour | 95 to 140 per hour | n/a | n/a | n/a | one-off changes |
Unused hours usually roll over for 1 to 3 months; after that they are lost. Get this in writing.
Reading an SLA without getting caught
The SLA (service level agreement) sets response time and fix time by severity. Many contracts advertise "4 hours", but that is the first response time, not the resolution. In the Netherlands you should also specify Dutch public holidays and the channel (ticket, chat, phone).
| Severity | Example | Response | Fix or workaround | Usual penalty |
|---|---|---|---|---|
| Blocking | cannot invoice, payments failing | 1 h | 4 to 8 h | 5% of retainer per day late |
| Major | a module is down, workaround possible | 4 h | 24 h | 2% per day |
| Minor | display error, incomplete export | 24 h | 5 business days | none |
| Change request | new field, new report | 48 h to estimate | per schedule | none |
| Security | published library vulnerability | 24 h | 72 h | 3% per day |
Also require a monthly report: hours used, tickets opened and closed, updates applied, backup restore test result. Without it, you cannot tell whether the retainer is undersized.
What no maintenance costs you
An application left unmaintained for 18 months accumulates 40 to 80 outdated libraries on average. Catching up in one go then costs 3 to 6 months of retainer. The most common scenario is still the Friday evening outage: without a contract, the original supplier is under no obligation to step in, and a new supplier will bill 2 to 5 days of code discovery before fixing anything.
Mini case study
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Daan, finance director of a medical supplies distributor in Amsterdam, had an order management and invoicing application built in 2024 for EUR 140,000, with no support contract. In 2026, a three-day outage blocks invoicing on revenue of EUR 45,000 per day: EUR 135,000 of delayed invoicing, plus EUR 9,000 paid in emergency to a freelancer. He signs a Standard retainer at EUR 3,000 per month, or EUR 36,000 per year (26% of the initial cost, above the usual 15-20% because invoicing is critical), plus EUR 7,000 of catch-up work in year one. A single two-day outage avoided covers the year's retainer.
FAQ
Is the original developer required to provide maintenance?
No, unless the development contract says so. A new supplier can take over after a handover audit of 5 to 10 days, billed EUR 6,000 to 14,000.
Are changes included in the retainer?
Small changes yes, within the included hours. Beyond 2 to 3 days of work, a change gets a separate quote.
What if we don't use our hours?
In most contracts they roll over for 1 to 3 months. If you use under 50% for 6 months, move to the lower plan.
What commitment period?
The standard is 12 months with 2 to 3 months' notice. A 24-month commitment often earns an 8 to 12% discount.
Is hosting included?
Rarely. Allow EUR 150 to 1,000 per month depending on load, with daily backups and an off-site copy.
Let's scope your project. Send us your application name, technology and number of users, and we will propose a handover audit and a retainer between EUR 1,500 and EUR 6,000 per month with a written SLA. 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.
