Awarding a subcontract to the wrong firm in the UK doesn't just create programme headaches — it can expose your business to adjudication claims, HSE enforcement, and now, direct liability under the Building Safety Act 2022. Yet most GCs still vet subcontractors through a mix of gut feel, outdated PQQ forms, and a quick check of a CSCS card on day one. That approach no longer holds up.
This guide covers what a robust subcontractor vetting process looks like today: from prequalification and CSCS compliance through to the new competence duties introduced by the Building Safety Act — and how to build these checks into your procurement workflow before a contract is ever signed.
Why Prequalification Is the First Line of Defence
Prequalification is not a box-ticking exercise. Done properly, it filters out firms that carry unacceptable financial, safety, or technical risk before you've committed a single pound to procurement. A specialist groundworks subcontractor on a £4.2m mixed-use scheme in Manchester, for example, should be able to demonstrate current EL/PL insurance at appropriate limits, a minimum three-year trading history, no County Court Judgements, and a verifiable track record on comparable projects.
Standard PQQ documentation should include:
- Company accounts for the last two financial years
- Employer's liability insurance (minimum £10m) and public liability (minimum £5m)
- Health and safety policy signed within the last 12 months
- RIDDOR incident rates for the past three years
- References from at least two comparable projects
- Evidence of relevant accreditations (CHAS, Constructionline, SafeContractor)
As we covered in our guide to mitigating subcontractor risk, the gap between a subcontractor's submitted PQQ and their actual operational capability is where most problems originate. Accreditation schemes like Constructionline Gold give a useful baseline, but they don't replace direct financial due diligence.
Don't Rely Solely on Accreditation Schemes
CHAS and Constructionline assess health and safety management systems, not financial solvency or project-specific competence. A subcontractor can hold Gold accreditation and still be trading insolvently. Always cross-reference with Companies House filings and credit reference data before award.
CSCS Compliance: What UK GCs Are Actually Responsible For
The Construction Skills Certification Scheme (CSCS) is the industry's primary mechanism for verifying that operatives hold the qualifications and training relevant to their role on site. Under CDM 2015, the Principal Contractor has a duty to ensure that all workers have the skills, knowledge, training, and experience to carry out their work safely. CSCS compliance is the most visible evidence of meeting that duty.
In practice, this means your subcontract conditions should require:
- All operatives to hold a valid CSCS card appropriate to their occupation
- Supervisors and site managers to hold a CSCS Manager or Supervisor card
- Evidence of card validity to be provided before site access is granted
- Immediate notification if a card expires or is revoked during the contract period
Spot checks are increasingly expected. On a £9.5m residential scheme in Bristol, a Principal Contractor was issued an Improvement Notice by the HSE after an operative was found working without a valid CSCS card — the subcontractor had submitted a compliant register at mobilisation but failed to update it when a card lapsed. The GC bore the enforcement action, not the sub.
Building Safety Act 2022: New Competence Duties You Cannot Ignore
The Building Safety Act 2022 introduced a statutory competence framework that goes significantly further than CSCS. For higher-risk buildings (HRBs) — broadly, residential buildings over 18 metres or seven storeys — the Act imposes duties on every party in the procurement chain, including subcontractors.
The Principal Contractor must now ensure that all contractors and subcontractors working on an HRB are competent for the work they are carrying out. Competence under the Act means both individual skills and organisational capability. This is not a self-declaration — you need documented evidence.
That suspension right is worth having in your subcontracts. Without it, you're relying on general termination provisions which trigger payment disputes and adjudication rights under the Housing Grants Construction and Regeneration Act 1996. As detailed in our guide to contract clauses every GC should red-line, the absence of specific competence enforcement mechanisms in subcontracts is one of the most common gaps we see on HRB projects.
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Building Vetting Into Your Procurement Workflow
Prequalification, CSCS verification, and Building Safety Act competence checks are only effective if they're embedded in your procurement process — not bolted on at mobilisation. The sequence matters.
Stage 1: Pre-Tender
Issue a PQQ alongside your RFQ. Require responses before any tender documents are released. This is also the right moment to confirm whether the project scope triggers HRB duties, which should be stated explicitly in your RFQ documentation so subcontractors self-select based on their actual competence.
Stage 2: Tender Evaluation
Evaluate PQQ responses before opening prices. A subcontractor who cannot demonstrate financial stability or Building Safety Act competence should not progress to bid evaluation regardless of their price. Conflating these stages is how commercially attractive but operationally unsuitable firms get awarded work.
Best Practice: Two-Envelope Tendering
Issue separate envelopes (or digital submissions) for technical/competence information and commercial pricing. Open technical submissions first and score them independently. Only open price envelopes for firms that meet the minimum competence threshold. This is standard on NEC4 frameworks and should be adopted more widely on JCT projects.
The Bottom Line
Subcontractor vetting in the UK has moved well beyond a phone call and a copy of a CSCS card. The Building Safety Act 2022 has created statutory competence obligations that run through the entire supply chain, CSCS compliance is a Principal Contractor liability, and prequalification gaps remain the most common route to financial and programme risk on site. A structured, sequenced vetting process — PQQ before tender, competence before price, documented evidence before award — is now the minimum standard for any GC working on regulated projects.
The contractual framework matters just as much as the vetting process itself. Your JCT or NEC4 subcontracts need to contain enforceable competence obligations, suspension rights tied to non-compliance, and clear audit provisions. If your current subcontract templates don't reflect the Building Safety Act's requirements, they are already out of date. Review them now, before the next award — not after the first enforcement notice lands.