Common Assessment Standard explained: the UK construction PQQ that replaced PAS 91

If a main contractor or a public-sector buyer has just asked you for the Common Assessment Standard (CAS), you've hit the scheme that's quietly become the default pre-qualification questionnaire (PQQ) for UK construction. It's broader than SSIP, it costs more than a basic health-and-safety accreditation, and — since March 2024 — it's the questionnaire central government and the wider public sector are told to use for higher-value works contracts. This guide explains what CAS actually is, who needs it, and how it sits alongside SSIP, Constructionline and CHAS.

What is the Common Assessment Standard?

The Common Assessment Standard is a standardised set of pre-qualification questions and matching assessment criteria for the UK construction industry. It was developed by Build UK in partnership with CECA and soft-launched in 2019. The point is simple: rather than every main contractor, framework or public buyer running their own bespoke PQQ, suppliers answer one industry-agreed question set, are audited against it once a year by a Recognised Assessment Body, and that certificate is then accepted by a growing list of contractors and clients.

CAS covers a much wider footprint than a health-and-safety scheme. The question set is structured into ten sections covering identity, financial information, health and safety, environmental management, quality, equal opportunities, modern slavery, anti-bribery and corruption, information security and — since Version 4 — building safety. For a section-by-section breakdown, see our Common Assessment Standard question set guide.

Who runs CAS and who issues the certificate?

Build UK owns and maintains the standard, but doesn't audit anyone itself. Certification is delivered by a network of seven Recognised Assessment Bodies (RABs) that have demonstrated their ability to audit suppliers against the standard. Following a Build UK update in late 2024, the RAB list is:

• CHAS (Veriforce CHAS) — via the CHAS Elite product
• Constructionline — via Gold or Platinum membership
• Achilles — Building Confidence product
• CQMS — Safety-Scheme
• Acclaim Accreditation (part of Supplier Assessment Services)
• Compliance Chain — Gold Supplier Membership (desktop only)
• SMAS Worksafe — SMAS Worksafe Pro (desktop only)

Build UK confirmed the addition of Compliance Chain and SMAS Worksafe in a December 2024 update, bringing the total to seven RABs. There is a data-sharing arrangement: a supplier who is certified by one RAB can authorise their data to be shared with another, so the same certificate becomes visible to more buyers without having to re-do the audit.

Why has CAS suddenly become important?

Two policy shifts pushed CAS from "nice to have" to "the default".

First, the British Standards Institution withdrew PAS 91 — the older standard PQQ — and central government replaced it. The Cabinet Office's Procurement Policy Note 03/24, published in March 2024, updated the Standard Selection Questionnaire and points contracting authorities at CAS. According to Constructionline's summary, for public-sector works contracts exceeding the £5.337 million threshold, CAS is the preferred pre-qualification method; below that threshold, it can be applied proportionately. PPN 03/24 is statutory guidance rather than a strict legal mandate, but in practice it means most central government departments and a lot of the wider public sector now ask for it on larger jobs.

Second, the Building Safety Act 2022 put new "organisational capability" duties on contractors. Build UK responded with CAS Version 4 in July 2024, adding a dedicated Building Safety section that lets a supplier evidence those duties through their CAS certificate. As Constructionline explains, many principal contractors now require their subcontractors to hold CAS — including the Building Safety questions — as a minimum.

How does CAS compare with SSIP, Constructionline and CHAS?

This is the bit that confuses most subcontractors. SSIP is a health-and-safety umbrella; the named schemes (CHAS, SafeContractor, SMAS, Acclaim, Constructionline) are products that sit underneath it. CAS is a different layer entirely — it's the PQQ, not the H&S accreditation, and most CAS products bundle SSIP H&S inside them.

For a deeper side-by-side of the scheme brands, see CHAS vs SafeContractor vs Constructionline and Constructionline Gold vs Silver vs Bronze. For the H&S layer, see SSIP mutual recognition explained.

What does CAS actually cost?

There is no single CAS fee, because the price depends on which Recognised Assessment Body you go through and which of their products carries the CAS audit. The two most common routes — and roughly where the typical small subcontractor lands — are Constructionline Gold and CHAS Elite. We keep current pricing in dedicated guides: Constructionline cost, CHAS cost and SafeContractor cost. Cheaper standalone H&S-only options are covered in the cheapest SSIP scheme, but note that those won't get you CAS — they only cover the H&S layer.

How do you get CAS-certified?

1. 1
   Pick a Recognised Assessment Body. Choose one of the seven RABs based on which buyers ask for which brand. If a main contractor specifically names "Constructionline Gold", use Constructionline; if they name "CHAS Elite", use CHAS. Otherwise the underlying CAS certificate is the same.
2. 2
   Choose desktop or site-based assessment. Build UK confirms two certification levels: desktop (document review) and site-based (assessor visits your premises). Smaller and lower-risk trades almost always go desktop; site-based is usually requested by clients who need extra assurance.
3. 3
   Pull together your evidence pack. Policies for H&S, environmental, quality, equal opportunities, modern slavery, anti-bribery, information security/GDPR, plus financial accounts, insurance certificates and Building Safety arrangements where in scope. Our CHAS documents checklist covers most of the same evidence.
4. 4
   Complete the question set. Build UK's industry-agreed question set is divided into ten sections covering thirteen risk areas. Your RAB hosts the questions in their portal; you answer once and upload evidence against each answer.
5. 5
   Audit and certification. The RAB audits your answers and evidence. On a pass you get a CAS certificate valid for 12 months. Renewal is annual — see accreditation renewal deadlines for how to stay on top of it.

What CAS doesn't fix

CAS removes a lot of duplication, but it doesn't make the rest of the accreditation circus disappear. Three honest caveats:

1. You may still need a separate SSIP certificate. Most main contractors still ask for an SSIP scheme by name (CHAS, SafeContractor, SMAS) on smaller works packages where CAS would be overkill. If you only hold CAS via a desktop RAB that doesn't bundle SSIP, you may end up needing both — see do I need more than one accreditation.
2. Buyers can still bolt on their own PQQ. A client can accept CAS for the standard questions and then add project-specific or framework-specific questions on top. CAS reduces, but doesn't eliminate, bespoke paperwork.
3. The annual renewal still has to be tracked. CAS certificates lapse after 12 months. Missing the renewal is the single most common way subcontractors fall off an approved-supplier list, and it's the residual pain we built TradeComply to address — a single tracker for renewal dates and re-used evidence across every scheme you hold.

Frequently Asked Questions

Is the Common Assessment Standard the same as SSIP?

No. SSIP is a mutual-recognition umbrella for health-and-safety pre-qualification schemes; CAS is a much broader PQQ standard covering finance, identity, quality, environment, modern slavery, information security and building safety, on top of H&S. Most CAS products (Constructionline Gold, CHAS Elite, Acclaim) bundle SSIP-recognised H&S inside them, so passing CAS via those routes also gives you SSIP-recognised H&S.

Is CAS legally required?

Not directly. CAS itself is an industry standard, not a statute. However, the Cabinet Office's Procurement Policy Note 03/24 is statutory guidance telling central government and the wider public sector to use CAS for pre-qualifying suppliers on works contracts above £5.337 million. In practice that makes it a hard requirement for most meaningful public-sector work above that threshold.

How long does CAS certification last?

Twelve months. Build UK confirms that certification is awarded once a year by a Recognised Assessment Body, and the certificate has to be renewed annually to remain valid. The renewal audit reuses most of your existing evidence but checks anything that's expired or changed.

What's the difference between CAS Version 4 and Version 5?

Version 4, launched in July 2024, introduced the dedicated Building Safety section aligned to the Building Safety Act 2022. Later versions of the standard have continued to refine and, in some areas, make Building Safety questions mandatory rather than optional. CAS is under regular review by Build UK, so the safest move is to confirm with your Recognised Assessment Body which version they're currently auditing against before you start.

If I'm certified by one Recognised Assessment Body, do other RABs automatically accept it?

Your CAS data can be shared between RABs through Build UK's data-sharing arrangement, which makes your certification visible to more buyers. But you only hold one CAS certificate from one RAB at a time — switching providers means a fresh application with the new body, not a transfer. This is one of the key differences between CAS and SSIP's formal mutual recognition.