The verdict in three sentences
To take over a web application after a vendor leaves, start with a takeover audit at EUR 3,000 to 8,000 excl. VAT: without it, no maintenance quote is reliable. Then, a support retainer (EUR 1,500 to 6,000 a month with an SLA from 4 h to 5 days) suits critical apps with a steady flow of requests, while time and materials (day rate EUR 550 to 800) suits occasional or highly variable needs. In every case, require a reversibility clause so it never happens again.
Step 1: the takeover audit
When the original vendor disappears (bankruptcy, termination, freelancer leaving), the IT director often inherits poorly documented code, outdated dependencies and incomplete access. The audit takes stock before any commitment.
| Area audited | What is checked | Indicative time | Risk if skipped |
|---|---|---|---|
| Access and ownership | Git repository, hosting, domains, third-party accounts | 0.5 to 1 day | Total lockout during an incident |
| Code quality | Structure, automated tests, technical debt | 1 to 3 days | Fixes take 2 to 3 times longer |
| Dependencies and versions | Framework, libraries, end-of-life PHP or Node | 0.5 to 1 day | Unpatched security flaws |
| Security | Authentication, injections, backups | 1 to 2 days | Data breach, GDPR fines |
| Documentation and deployment | Procedures, environments, scripts | 0.5 to 1 day | Risky releases |
| Report and remediation plan | Costed priorities over 3 to 12 months | 1 day | Underestimated support budget |
For a mid-sized application (20,000 to 60,000 lines of code), the audit takes 5 to 10 days, so EUR 3,000 to 8,000. It often reveals an initial upgrade of EUR 5,000 to 20,000 to handle before maintenance can stabilise.
Step 2: retainer or time and materials
| Criterion | Support retainer | Time and materials | Prepaid day bundle |
|---|---|---|---|
| 2026 cost | EUR 1,500 to 6,000 per month | Day rate EUR 550 to 800 | 10 to 20 days a year, rate cut 5 to 10% |
| Fix SLA | 4 h (critical) to 5 days (minor) | Subject to availability, rarely guaranteed | Often 1 to 3 days |
| Budget predictability | High | Low | Medium |
| Enhancements included | Small changes within a quota | All, billed by time | Against the day balance |
| Best for | Critical app, more than 5 requests a month | Under 3 days of need a month | Moderate use, fixed annual budget |
| Governance | Monthly review, SLA metrics | Approval of each task | Balance tracking |
| Commitment | 12 to 36 months | None | 12 months |
A well-built retainer separates three levels: corrective maintenance (bugs, with an SLA per severity), preventive maintenance (security updates, version upgrades) and an enhancement quota, for example 2 days a month, beyond which work is quoted separately.
Step 3: lock down the contract
The reversibility clause is the main lesson of a forced takeover. It covers handover of source code and up-to-date documentation, a 1 to 3 month transition plan priced at signature, and ownership of all accounts (hosting, domain, third-party services) in the company's name. Add measurable indicators: SLA compliance rate (target 95%), average fix time, number of production incidents. A penalty of 5 to 10% of the monthly fee for missed SLAs is reasonable.
Mini case study
Thomas, IT director of a 180-person distribution company, takes over a B2B ordering portal after his vendor goes into liquidation. The application handles EUR 2 million of orders a year.
- Takeover audit: EUR 6,000, upgrade identified at EUR 14,000 (end-of-life framework)
- Estimated need: 4 days a month of fixes and enhancements
- Time and materials: 4 × EUR 700 × 12 = EUR 33,600 a year, no guaranteed SLA
- Retainer: EUR 3,200 a month, so EUR 38,400 a year, 4 h SLA on blocking bugs and 2 enhancement days included
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One day of portal downtime means about EUR 8,000 of delayed or lost orders. Thomas picks the retainer: EUR 4,800 more a year for a 4 h SLA, recovered as soon as a single outage is shortened by half a day.
FAQ
How much does a web app support retainer cost?
EUR 1,500 to 6,000 excl. VAT a month depending on criticality, app size and enhancement quota. A mid-sized business app often sits around EUR 2,500 to 3,500.
What day rate for time and materials in 2026?
Budget EUR 550 to 800 a day for a mid-level or senior developer in markets like Amsterdam or Strasbourg. Architecture experts can exceed EUR 900.
Is the takeover audit really necessary?
Yes, it drives all pricing: without it, vendors add a 20 to 30% risk margin. It costs EUR 3,000 to 8,000 and takes 2 to 3 weeks.
What should the reversibility clause include?
Handover of code and documentation, a 1 to 3 month transition plan priced in advance and account ownership in the client's name. It avoids paying for a full audit again at the next change.
Can we start on time and materials and switch to a retainer?
Yes, and it is recommended: 3 months of time and materials measure the real request volume. The retainer is then sized on data, not on an estimate.
Let's scope your project. Give us read access to your application or describe its stack and usage: we will price the takeover audit, the right retainer or time and materials model and the transition schedule. 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.
