Web Application Penetration Test Pricing in London (2026)

The verdict in three sentences

A grey-box penetration test of a web application costs GBP 5,500 to GBP 16,000 in London in 2026, for 5 to 12 days of testing at a day rate of GBP 900 to GBP 1,300. It is the document enterprise security teams ask for before signing with a scale-up, with a report aligned on the OWASP Top 10 and a retest at GBP 1,300 to GBP 2,600 to prove remediation. For the public sector or critical operators, plan for CREST or CHECK accredited testers, 15% to 30% more expensive.

Black, grey or white box: choosing the scope

Price depends first on scope: number of user roles, APIs, sensitive functions (payments, data export, admin) and how much information the tester receives.

For a B2B SaaS with three roles and a public API, grey box offers the best cost to coverage ratio: the tester checks privilege escalation between tenants, the main risk in a multi-tenant architecture.

Standard firm or accredited testers

CREST accreditation is not mandatory for a private client, but many enterprise buyers ask for it, and UK government work typically requires CHECK. Most private enterprises accept a recognised firm with a documented methodology.

Lead time is often the real bottleneck: book the slot as soon as the signing date is known.

What a good report contains

A report useful to a buyer contains a non-technical executive summary, the list of vulnerabilities ranked by severity (CVSS score), their OWASP Top 10 mapping, proof of exploitation and a prioritised remediation plan. In practice, an application that has never been tested often surfaces 2 to 5 critical or high findings, most commonly broken access control, injection and misconfiguration.

Mini case study

Oliver, CTO of a London scale-up selling HR SaaS, must provide a pentest report to a FTSE 100 group before signing a GBP 210,000 annual contract. He orders an 8-day grey-box test at GBP 1,000, i.e. GBP 8,000, then a 2-day retest at GBP 2,000. The report reveals 3 high findings, fixed by the team in 6 development days at an internal cost of about GBP 3,100. Total cost: GBP 13,100, or 6.2% of the contract's first year, and a report reusable for the next three tenders.

FAQ

How much does a web application penetration test cost in London in 2026?

Between GBP 5,500 and GBP 16,000 for grey box, covering 5 to 12 testing days. An API-only test starts around GBP 3,000.

Do we need CREST or CHECK testers?

Only if the client is public sector, a critical operator or requires it contractually. Expect 15% to 30% more and 3 to 8 weeks of lead time.

Is the retest essential?

Yes, it proves to the client that findings are fixed. It costs GBP 1,300 to GBP 2,600 for 1 to 2 days.

How far before launch should we schedule the test?

Ideally 4 to 6 weeks before go-live: 1 to 2 weeks of testing, 1 to 2 weeks of fixes, then the retest.

How often should we repeat it?

Once a year and after any major change (new payment module, new public API). Many enterprises ask for a report less than 12 months old.

Let's scope your project. Describe your application, its user roles and target signing date: we will scope the test, the remediation work and an indicative budget with our security partners. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.