The verdict in three sentences
For a 200-employee services SME whose line-of-business app runs invoicing and scheduling, an application maintenance contract costs roughly £700 to £5,500 a month in London, and the difference comes down to three clauses: response time, enhancement days included and exit terms. A credible SLA promises a 4 business-hour response on critical incidents, a fix or workaround within 1 business day, and priced service credits. Without a documented exit plan, you stay locked in whatever the headline price.
The three maintenance levels on the London market
The IT director of a 200-employee services firm based in Shoreditch must renew the maintenance contract for a management app built 6 years ago. The original supplier was acquired, response times are slipping, and the board wants a clear contract before the next financial year.
| Level (2026 estimate) | Monthly fee (excl. VAT) | Critical incident response | Enhancements included | Typical fit |
|---|---|---|---|---|
| Corrective only | £700 to £1,300 | 1 business day | none, time and materials at £600 to £800 a day | stable app, few users |
| Corrective + preventive | £1,300 to £2,600 | 8 business hours | 5 days per quarter | core app, 50 to 150 users |
| Full application maintenance | £2,600 to £5,500 | 4 business hours | 10 to 15 days per quarter | critical app, 150+ users |
| Out-of-hours on-call add-on | + £450 to £1,300 | 2 h outside business hours | not applicable | 7-day operations |
| Managed hosting add-on | + £180 to £1,000 | depends on host | not applicable | dedicated servers or cloud |
For 200 employees with 120 daily users, the middle tier is often enough, as long as unused enhancement days roll over by one quarter.
SLA clauses to check one by one
An SLA is only as good as its definitions. Check that severity is defined by business impact (invoicing blocked = critical), that the clock starts when the ticket is logged and not when the supplier triages it, and that service credits are capped at a meaningful level.
| Clause | Recommended value | Common trap |
|---|---|---|
| Critical incident response | 4 business hours | clock starts after triage |
| Critical fix or workaround | 1 business day | only response time committed |
| Major incident | 8 h response, 3-day fix | supplier decides severity |
| Service credits | 5% of the monthly fee per breach, capped at 20 to 30% | 5% cap with no real effect |
| Availability (if hosted) | 99.5% monthly | unlimited planned maintenance excluded |
| Reporting | monthly report + quarterly review | no measured KPIs |
| Exit plan | written plan, 3 months of handover, up-to-date docs | on request, billed at day rates |
| Code ownership | code and Git repository owned by the client | code held by the supplier |
The exit plan deserves attention: require permanent access to the code repository, architecture and operations documentation updated with every release, and a priced 30 to 60 day handover plan agreed at signature. UK GDPR also requires a data processing agreement covering where data is hosted and how it is returned.
How Kolonell works
Kolonell takes over maintenance of existing business apps after a code and infrastructure audit. For apps we build, monthly maintenance is 35,000, 75,000 or 120,000 FCFA per month (53, 114 or 183 EUR) depending on the service level; a maintenance contract with a committed SLA, on-call and quarterly enhancement days is quoted after the audit. When an app is too fragile to maintain, a custom rebuild costs 4,000,000 to 7,000,000 FCFA (6,100 to 10,670 EUR) for medium complexity and 7,000,000 to 15,000,000+ FCFA (10,670 to 22,870+ EUR) for high complexity.
Mini case study
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Emma, IT director of a 200-employee services SME in London, compares two offers for her management app:
- Offer A: £1,050 a month, corrective only, enhancements at £700 a day. Her historical need is 36 enhancement days a year, so 12,600 + 25,200 = £37,800 a year.
- Offer B: £2,500 a month with a 4-hour response and 10 enhancement days per quarter included, 40 days a year. Cost: £30,000 a year.
Offer B costs £7,800 less over the year, commits to 4 hours instead of 1 day, and leaves 4 spare enhancement days. An invoicing outage lasting one extra day delays about 180 invoices, so the shorter SLA also has a direct cash effect.
FAQ
How long does it take to switch maintenance supplier?
Allow 2 to 3 months: one month of audit and knowledge transfer, then 1 to 2 months of parallel running. A 3-month notice period in the current contract is common.
What happens to unused enhancement days?
Negotiate a rollover to the next quarter, capped at 50% of the volume. Without rollover, firms waste about 25% of the days on average.
Does maintenance include security updates?
It should: framework, dependency and system updates at least quarterly, and within 72 h for a critical vulnerability. Get it written explicitly into preventive maintenance, which also helps with Cyber Essentials.
Is a fixed monthly fee better than time and materials?
Above 25 to 30 enhancement days a year, a fixed fee is usually 10 to 20% cheaper. Below that, corrective-only plus day rates stays competitive.
Let's scope your project. Share your app, your incident volumes and the response times you need, and we will propose an audit followed by a fitting maintenance contract. 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.
