The verdict in three sentences
A line-of-business web application with no maintenance contract is an operational risk, especially when the freelancer who built it has left without documentation. For a London company, taking it over starts with a handover audit of 3,000 to 6,000 GBP, then a retainer of 1,500 to 5,000 GBP a month, in line with the usual benchmark of 15 to 20 % of the initial build cost per year. The contract must state in writing a 4-hour response time for a critical incident, or it protects nothing.
What application maintenance costs by service level
Application maintenance covers three kinds of work: corrective (fixing defects), preventive (security updates, version upgrades) and evolutive (small enhancements). Price depends mainly on application size and guaranteed response times.
| Plan (2026 estimate, excl. VAT) | Essential | Standard | Critical |
|---|---|---|---|
| Monthly retainer | 1,500 to 2,200 GBP | 2,500 to 3,800 GBP | 4,000 to 5,000 GBP |
| Application covered (initial cost) | up to 80,000 GBP | 80,000 to 200,000 GBP | 200,000 GBP and above |
| Enhancement days included per month | 0.5 day | 1 to 2 days | 2 to 3 days |
| Response time, critical incident | 8 business hours | 4 business hours | 4 hours, 24/7 |
| Response time, major incident | 2 business days | 1 business day | 8 hours |
| Security and dependency updates | quarterly | monthly | monthly plus urgent patches within 48 h |
| Monitoring and backups | daily | daily, restore test every 6 months | real time, quarterly restore test |
| Target availability | 99 % | 99.5 % | 99.9 % |
A company whose application runs orders, member services or staff scheduling usually sits in the Standard plan. Critical is justified when downtime blocks deliveries or payments the same day.
Taking over an orphan application: audit first
Taking over an undocumented application without auditing it means signing response-time commitments on unknown code. No serious provider does that. A handover audit takes 5 to 10 days and delivers a costed assessment.
| Audit item | What we check | Common risk on a freelancer-built app |
|---|---|---|
| Access and ownership | code repository, hosting, domain, cloud accounts | accounts in the freelancer's name, passwords lost |
| Technical versions | framework, language, database | version out of support for over 2 years |
| Security | vulnerable dependencies, password handling, backups | no tested backup |
| Code quality | automated tests, readability, duplication | test coverage below 10 % |
| Documentation | setup, architecture, business rules | none |
| UK GDPR compliance | records of processing, retention, processors | customer data with no deletion policy |
| Remediation plan | prioritised, costed phases | 5 to 20 days of catch-up before maintenance starts |
The audit costs 3,000 to 6,000 GBP depending on size. It is often followed by remediation of 5,000 to 18,000 GBP, after which the monthly retainer becomes predictable.
Mini case study
James, Head of IT at a London cooperative wholesaler, runs an order management application built for 110,000 GBP by a freelancer who left 8 months ago. During the last outage, orders were blocked for 2 days, and the company paid emergency support at 1,000 GBP a day plus 7,000 GBP in late-delivery penalties to a retail customer. He commissions an audit at 4,500 GBP, remediation at 10,000 GBP, then a Standard retainer at 2,800 GBP a month, or 33,600 GBP a year, about 30 % of the initial cost in year one, falling toward 20 % once the app is stable and the retainer is reduced. Avoiding a single 2-day outage a year already saves 9,000 GBP, before counting the enhancement days included.
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FAQ
What is the difference between application maintenance and basic support?
Support answers user questions. Application maintenance commits the provider on the code itself: defect fixes, security updates and small enhancements, with contractual response and resolution times.
Is a 4-hour response time for a critical incident realistic?
Yes, in business hours, for response and a workaround. A permanent fix can take 1 to 2 days. The contract should distinguish response time, workaround time and resolution time.
What happens if the provider misses its SLA?
A serious contract sets service credits, often 5 to 10 % of the monthly retainer per breach, capped at 20 to 30 % of the retainer. It also includes an exit and transition clause so you can switch provider.
Can we recover an app if the freelancer no longer responds?
Yes, if the company holds the hosting or the domain. The audit starts by recovering access. With no access at all, recovery can take 2 to 6 weeks via the hosting provider and registrar.
Are enhancements included in the retainer?
Plans include 0.5 to 3 enhancement days a month. Beyond that, work is billed by the day, around 600 to 850 GBP in London in 2026 for a senior developer.
Let's scope your project. Describe your application, its technology and how critical it is, and we will price the handover audit, the right maintenance plan and the takeover timeline. 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.
