The verdict in three sentences
A web application security audit (pentest) runs between 10,000 and 25,000 GBP in London in 2026, depending on the attack surface and test depth. Expect 2 to 4 weeks with OWASP Top 10 testing, a prioritised report, a remediation plan and a retest included. A single critical flaw fixed before go-live avoids an incident costing between 50,000 and 200,000 GBP (data breach, ransom, downtime, penalties).
What an application pentest covers
A serious audit combines automated and manual testing on authentication, access rights, injections, business logic and configuration. Price depends on the number of roles, endpoints and the level (black, grey or white box).
| Audit type | Scope | 2026 price (GBP) | Timeline |
|---|---|---|---|
| Targeted pentest | 1 app, 1-2 roles, black box | 10,000 - 13,000 | 2 wks |
| Standard pentest | App + API, grey box | 14,000 - 19,000 | 3 wks |
| In-depth pentest | + Code review, white box | 20,000 - 25,000 | 4 wks |
| Continuous audit | Recurring quarterly tests | 6,000 - 10,000/qtr | Recurring |
| Remediation retest | Verify fixes | Included / +2,000 | +1 wk |
A senior pentester's day rate in London ranges from 900 to 1,400 GBP in 2026. A standard pentest represents 12 to 18 person-days including report and retest.
The cost of an incident avoided
An audit budget should be compared to the cost of an incident, not to zero. In 2026, a security incident at an SME becomes expensive as soon as it touches customer data.
| Incident type | Estimated direct cost 2026 | Additional impacts |
|---|---|---|
| Customer data breach | 50,000 - 120,000 GBP | GDPR fine, loss of trust |
| Ransomware | 80,000 - 200,000 GBP | Multi-day business halt |
| Defacement/downtime | 10,000 - 40,000 GBP | Reputation, SEO |
| Business-logic fraud | 20,000 - 150,000 GBP | Direct financial loss |
| Account takeover | 15,000 - 60,000 GBP | Support, customer notices |
Mini case study
Karim, CISO of an e-health SME in London (a platform handling patient data), had to validate security before go-live. He commissioned a standard grey-box pentest at 15,000 GBP, delivered in 3 weeks, retest included.
The audit revealed a critical access-control flaw letting one user view other patients' records. Fixed before launch, it would otherwise have exposed the company to a breach estimated between 50,000 and 120,000 GBP in direct costs, on top of a GDPR fine and lost hospital contracts. Audit cost: 15,000 GBP; incident avoided: at least 50,000 GBP. The benefit/cost ratio exceeds 3 to 1 on this single flaw.
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FAQ
Black, grey or white box: which to choose?
Grey box (with a few test accounts) offers the best coverage/price ratio for most SMEs. White box, with code review, is justified for critical or regulated applications.
Is the retest included?
With most serious providers, a fix-verification retest is included within a 4 to 8 week window. Check it in the quote.
How often should we audit?
At minimum before each major go-live, then once a year. Sensitive applications benefit from a continuous quarterly audit from 6,000 GBP/quarter.
What does the report contain?
A list of vulnerabilities prioritised by criticality (CVSS), proof of exploitation, business impact and concrete remediation recommendations your developers can act on.
Does an audit guarantee zero flaws?
No audit guarantees zero risk, but an OWASP pentest sharply reduces the attack surface and proves your due diligence for audits or cyber insurance.
Let's scope your project. Tell us your application type, number of roles and target go-live date, and we will scope an audit between 10,000 and 25,000 GBP. 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.
