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The Common Assessment Standard Explained: What UK Contractors Need to Know

By Brian Crocker· Last reviewed: 2 September 2026

Corrected on 2026-09-02: an earlier version of this guide stated in bold that PPN 03/24 "does not mention the Common Assessment Standard at all", and told readers to cite Build UK instead. That was wrong. PPN 03/24, Annex A, paragraph 14 reads: "For works contracts, including the procurement of mixed contracts that include supplies and services, contracting authorities should use the Common Assessment Standard (CAS), in place of the standard SQ template in pre-qualification of bidders." Corrected against the published Cabinet Office PDF; the PPN section below now quotes it.

Also corrected on 2026-09-02: the Building Safety Act section previously described higher-risk buildings as "over 18 metres" and put the 7-storey test on residential buildings only, and said the Building Safety Regulator was "part of the HSE". Both were wrong. Section 120D(2) of the Building Act 1984 reads "at least 18 metres in height or has at least 7 storeys" and applies that test to every specified description — so a building of exactly 18 metres, and a 7-storey care home under 18 metres, are both in scope. The BSR sat within the HSE only until 27 January 2026, when SI 2026/20 established it as a separate body corporate. Corrected against legislation.gov.uk.

Also corrected on 2026-09-02: this guide previously described CAS as "structured in modules, divided into core criteria and additional modules" and called the health and safety part "the CAS core criteria" that "every SSIP assessment must check". Build UK, which owns CAS, uses neither term: it publishes CAS as "an industry-agreed question set and corresponding assessment standards" with two certification levels, desktop and site-based. "Core Criteria" is SSIP's term for its own health and safety threshold standard, and SSIP is explicit that it "does not currently include an assessment against the Building Safety Act or other elements of the Common Assessment Standard [CAS]". The relationship is narrower than the earlier wording implied: a valid SSIP assessment exempts you from CAS Section 4 (Health & Safety) only. Corrected against Build UK and SSIP.

If you hold an SSIP accreditation, you have been assessed against the SSIP Core Criteria. That is not the same thing as the Common Assessment Standard, and the difference costs contractors money: CAS is a broader question set that sits above the health and safety core, and most entry-level scheme tiers do not include it. CHAS lists "Meet Common Assessment Standard requirements" as included at Elite only, and Constructionline defines Gold as "all the benefits of Silver membership and also meet the Common Assessment Standard".

CAS matters more than it used to because of where public-sector buyers are being pointed. Build UK states that "Central Government departments and wider public sector bodies should use the Common Assessment Standard to pre-qualify suppliers in accordance with PPN 03/24." For contractors who work in or want to work in the public sector, understanding CAS has moved from optional to necessary.

This guide explains what CAS is, how it is structured, which accreditation tiers satisfy it, and what PPN 03/24 means for your business.

What Is the Common Assessment Standard?

The Common Assessment Standard (CAS) is the construction prequalification framework developed by Build UK in partnership with Constructionline and the SSIP (Safety Schemes in Procurement) schemes. It defines a standardised set of assessment criteria that Build UK's recognised assessment bodies certify contractors against.

The Common Assessment Standard replaced PAS 91, the older BSI prequalification specification. BSI's catalogue record for PAS 91:2013+A1:2017 gives its status as "Withdrawn" with a withdrawal date of "21 Apr 2023" (verified 2 September 2026). For context on PAS 91 and the transition, see our guide: PAS 91 Is Withdrawn: What Replaced It.

Build UK describes it as "an industry-agreed question set and corresponding assessment standards for the pre-qualification of suppliers". Build UK recognises seven assessment bodies to certify against it: Achilles, Compliance Chain, Constructionline, CQMS, SCCS, Smas Worksafe and Veriforce CHAS.

A separate mechanism handles health and safety alone: every SSIP Registered Member assesses against the SSIP Core Criteria, which is what makes SSIP mutual recognition possible. CAS is the wider prequalification question set layered on top, and the two connect at exactly one point — SSIP states that "any valid SSIP assessment completed by any of our member schemes and visible on the SSIP portal will provide exemption against Section 4 of the CAS", the health and safety section. Everything else in CAS still has to be assessed. Keeping the two apart is the single most useful thing to take from this guide, because a client asking for "SSIP" and a client asking for "CAS" are asking for different tiers of the same schemes.

The current question set is Version 5 (Build UK, verified September 2026) — Build UK publishes "a guide to the question set (Version 5) … to help companies prepare for an audit". It includes a dedicated Building Safety section covering organisational capability under the Building Safety Act 2022. Version 6 is due on 1 November 2026, so if you are planning an assessment around that date, check which question set your assessment body will be using.

For an overview of SSIP and how mutual recognition works in practice, see our guide: What Is SSIP and Which Scheme Should You Choose?.

How CAS Is Structured

CAS is not a single pass/fail assessment. Build UK publishes it as "an industry-agreed question set and corresponding assessment standards", certified at two levels — desktop and site-based — with companies choosing the level appropriate to their trade, size and client requirements. The question set covers health and safety alongside a wider set of compliance areas, both described below.

Health and Safety: CAS Section 4

Health and safety sits in Section 4 of the CAS question set, and it is the one part of CAS a valid SSIP certificate can exempt you from. SSIP publishes the mapping itself: a valid SSIP assessment provides exemption against "Common Assessment Standard: Section 4: Health & Safety (questions 135-173)". The underlying standard aligns to UK health and safety legislation — primarily the Health and Safety at Work etc. Act 1974, the Management of Health and Safety at Work Regulations 1999, and the Construction (Design and Management) Regulations 2015 (CDM 2015).

The health and safety ground an assessor covers:

  • Health and safety policy — A written policy signed by a senior individual, reviewed within 12 months, with statement of intent, organisation of responsibilities, and practical arrangements.
  • Risk assessment — Evidence of a systematic process for identifying hazards, assessing risks, and implementing controls. Must cover the contractor's specific activities.
  • Training and competence — Records demonstrating workforce competence: CSCS, SMSTS/SSSTS, trade qualifications, ongoing training, and toolbox talks.
  • Monitoring and review — Evidence that health and safety arrangements are monitored, reviewed, and improved. Not just paperwork — active management.
  • Accident and incident reporting — Procedures aligned to RIDDOR 2013 (Reporting of Injuries, Diseases and Dangerous Occurrences Regulations), with evidence of investigation and corrective action.
  • Insurance — Current employers' liability insurance (minimum £5 million, the amount prescribed by reg 3(1) of the Employers' Liability (Compulsory Insurance) Regulations 1998 under the Act of the same name) and public liability insurance.
  • Competent advice — Access to competent health and safety assistance as required by Regulation 7 of the Management of Health and Safety at Work Regulations 1999.
  • Subcontractor management — Procedures for vetting and managing subcontractors' health and safety competence.

Every SSIP scheme that actually carries out assessments — CHAS, SafeContractor, SMAS, Once For All Health & Safety, CQMS, and the other Registered Members — assesses against the SSIP Core Criteria, which cover this same ground. (Constructionline is listed by SSIP as a Supporter Member, not a Registered Member: the SSIP assessment inside a Constructionline membership is delivered by Once For All Health & Safety.) If you hold any SSIP accreditation, you have been assessed against the SSIP Core Criteria — the health and safety threshold CAS builds on, not CAS itself.

For a detailed breakdown of what assessors check across all documentation areas, see our guide: Construction Accreditation Requirements.

Beyond Health and Safety

The rest of the CAS question set covers compliance areas that are increasingly expected by clients and procurers — and that an SSIP certificate does not touch. SSIP says so directly: its Core Criteria confirm "organisational capability against Health and Safety legislation" and this "does not currently include an assessment against the Building Safety Act or other elements of the Common Assessment Standard [CAS] such as Environmental, Equality, Modern Slavery or Anti-Bribery". Those areas are:

  • Environmental management — Environmental policy, waste management procedures, pollution prevention, and awareness of environmental responsibilities.
  • Quality management — Documented procedures for quality control, inspection, defect management, and continuous improvement.
  • Equal opportunities and diversity — Compliance with the Equality Act 2010, written policy, fair recruitment practices, and grievance procedures.
  • Modern slavery — Due diligence on supply chain labour practices, right-to-work verification, and a proportionate modern slavery statement (aligned to the Modern Slavery Act 2015).
  • Anti-bribery and corruption — Policy and procedures aligned to the Bribery Act 2010.
  • Financial standing — Evidence of financial stability and ability to fulfil contractual obligations.

Not every accreditation tier covers all of this. This is where the distinction between "basic" and "full" CAS compliance matters — and where many contractors get caught out.

Which Accreditation Tiers Satisfy CAS?

This is the question that matters commercially. The answer depends on how much of the CAS question set a particular accreditation tier assesses.

Tiers that do NOT include CAS (core SSIP health and safety only)

The following entry-level tiers give you an SSIP health and safety certificate, not CAS certification:

  • CHAS Standard
  • Constructionline Silver
  • SafeContractor (standard)
  • SMAS Worksafe
  • Once For All Health & Safety, formerly Acclaim (standard)

These give you SSIP mutual recognition for health and safety. For many contracts that is sufficient — but if a PQQ names the Common Assessment Standard, none of them answers it.

Tiers that do include CAS

Build UK publishes two levels of CAS certification: "There are two levels of certification: desktop and site-based. Companies apply to a Recognised Assessment Body for the certification level that is most appropriate for their business based on a range of factors including trade, size and the requirements of their clients."

The scheme tiers that include CAS:

  • CHAS Elite — the CHAS package listed as meeting "Common Assessment Standard requirements". Standard and Advanced are listed as not including it.
  • Constructionline Gold — "all the benefits of Silver membership and also meet the Common Assessment Standard". Constructionline states that Gold covers the CAS desktop assessment.
  • Constructionline Platinum — Gold plus "a one day premises audit", which is the site-based route.
  • Achilles BuildingConfidence — Achilles is one of Build UK's recognised assessment bodies.

Scheme tier names and CAS mappings change. Check the scheme's own published packages page before relying on a mapping here.

For a comparison of CHAS, Constructionline, and SafeContractor tiers, see our detailed comparison guide. For more on Constructionline Gold specifically, see our Constructionline Gold guide.

The Building Safety Act 2022 Section

The question set includes a section reflecting the Building Safety Act 2022 (BSA 2022). The BSA 2022 established a new regulatory regime for higher-risk buildings in England. Section 120D(2) of the Building Act 1984 defines a higher-risk building as one that "is at least 18 metres in height or has at least 7 storeys" and is "of a description specified in regulations made by the Secretary of State"; regulation 2 of SI 2023/275 specifies "a building which contains at least two residential units", "a care home" and "a hospital". The height-or-storeys test applies to all three descriptions equally — so a building of exactly 18 metres is in scope, and so is a 7-storey care home below 18 metres. The BSA 2022 also created the Building Safety Regulator, which sat within the Health and Safety Executive until 27 January 2026; on that date SI 2026/20 established it as a separate body corporate ("A body corporate called the Building Safety Regulator is established"). The Act also imposed new duties on dutyholders throughout the building lifecycle.

The CAS Building Safety section assesses whether contractors working on higher-risk buildings understand and comply with their BSA duties. Build UK does not tie this section to a particular version number, so treat it as part of the current question set rather than a versioned add-on. For contractors who do not work on higher-risk buildings, this section may not apply. But for those who do — or who want to — it adds a new layer to the accreditation assessment.

If your work involves residential buildings at height, understanding CDM 2015 duties is already foundational. See our guide: CDM 2015 Duties for SME Contractors.

PPN 03/24: Why CAS Now Matters More

Procurement Policy Note 03/24 was published by the Cabinet Office in March 2024. PPNs are instructions to public-sector buyers on how to conduct procurement. They carry significant weight — while not primary legislation, government departments and other contracting authorities are expected to follow them.

Be precise about what PPN 03/24 itself says. In its own words, it "updates the Selection Questionnaire (SQ) and accompanying statutory guidance", and it applies to contracting authorities "when undertaking above threshold procurements within part 2 of the Public Contracts Regulations 2015 (PCR 2015)". It also names the Common Assessment Standard directly, and tells buyers to use it. Annex A, paragraph 14 reads:

"For works contracts, including the procurement of mixed contracts that include supplies and services, contracting authorities should use the Common Assessment Standard (CAS), in place of the standard SQ template in pre-qualification of bidders. However, it will be for individual contracting authorities to ensure the questions used are relevant and proportionate to the contract being procured, ensure equivalent standards are permissible and a level playing field for all types of suppliers."

Two things follow from the wording. The instruction is scoped to works contracts — including mixed contracts that also cover supplies and services — rather than to every procurement. And it is qualified: the PPN leaves each contracting authority to keep the questions "relevant and proportionate" and to permit equivalent standards, so it is a direction with discretion attached, not a blanket rule.

Build UK states the same expectation in its own words: "Central Government departments and wider public sector bodies should use the Common Assessment Standard to pre-qualify suppliers in accordance with PPN 03/24." That is an accurate restatement of the PPN, not a substitute for it. If a client asks where the expectation comes from, the strongest answer is Annex A paragraph 14 of the PPN itself, with Build UK's sentence as the plain-English version. In practical terms:

Public sector construction buyers are pointed at CAS for prequalification. The PPN tells contracting authorities to use CAS in place of the standard SQ template on works contracts, and Build UK restates that position.

CAS certification, not just an SSIP certificate, is increasingly expected. Buyers may require evidence against the wider CAS question set (environmental, quality, equality, modern slavery, anti-bribery) rather than health and safety alone.

Basic-tier accreditation may not be sufficient. If a public sector buyer requires evidence of the Common Assessment Standard, holding CHAS Standard or Constructionline Silver will not satisfy the requirement — neither includes CAS. You would need CHAS Elite, Constructionline Gold or above, or certification from another Build UK recognised assessment body.

Important caveats: this is statutory guidance addressed to public sector buyers, not a requirement imposed directly on contractors, and paragraph 14 itself leaves the questions to each authority's judgement of what is "relevant and proportionate". Adoption is still being rolled out across contracting authorities, and the pace of implementation varies. Note also that PPN 03/24 is framed around PCR 2015, while the Procurement Act 2023 regime applies to procurements commenced on or after 24 February 2025 — so which rules govern a given tender depends on when it was advertised. Check the specific prequalification requirements for each contract you are targeting rather than assuming a general rule applies.

The practical effect is that CAS certification is increasingly expected for public sector construction work. For contractors who want to be well positioned as adoption widens, acting early is prudent — but it is not yet a universal gate.

For context on how PAS 91 prequalification questionnaires relate to CAS, see our PAS 91 guide.

What This Means for Your Business

If you only work in the private sector and your clients do not require CAS-level accreditation, the immediate impact is limited. Your existing SSIP accreditation — at whatever tier — continues to serve its purpose.

If you work in public sector construction, or plan to, here is what to act on:

1. Check Your Current Accreditation Level

Do you hold a core SSIP health and safety certificate only (CHAS Standard, Constructionline Silver, SafeContractor) or a tier that includes CAS (CHAS Elite, Constructionline Gold or Platinum, an Achilles BuildingConfidence Gold CAS tier)? If it is SSIP only, you may need to upgrade.

2. Review Your Target Contracts

Look at the prequalification requirements for the public sector contracts you are targeting. Are they referencing CAS? Are they requiring evidence of environmental, quality, equality, and modern slavery compliance? If yes, basic-tier accreditation will not get you through the gate.

3. Prepare for the Non-Health-and-Safety Areas

If you need to move from a core SSIP certificate to a CAS-inclusive tier, you will need to prepare additional documentation: environmental policy and procedures, quality management procedures, equal opportunities policy, modern slavery statement, and anti-bribery policy.

This is not as onerous as it sounds for most established SMEs. Many already have some of these documents in place — they just have not been assessed against them. The gap is often one of documentation and formalisation rather than fundamental capability.

4. Budget for the Upgrade

Moving from CHAS Standard (from £429 a year) to CHAS Elite (from £949), or from Constructionline Silver to Gold, involves higher fees. Factor this into your annual accreditation budget. For a detailed cost comparison, see our Construction Accreditation Costs guide.

5. Assess Your Readiness

Before committing to an upgrade, benchmark your current position. Use the Construction Accreditation Readiness Scorer to identify gaps in your documentation and management systems.

The Silent Standard

CAS has been shaping construction accreditation for years. Most contractors who hold SSIP accreditation have been assessed against CAS criteria without thinking about it in those terms. The framework worked quietly in the background, ensuring consistency across schemes.

Build UK's direction of public-sector buyers towards CAS has brought it into the foreground. For contractors working in public sector construction, CAS certification is becoming explicit rather than implied. The contractors who already hold a CAS-inclusive tier — CHAS Elite, Constructionline Gold or above, or equivalent — are well positioned. Those holding a core SSIP certificate need to understand the gap and plan accordingly.

The standard itself is not new. The requirement to demonstrate compliance with it is.

For the broader context on prequalification in UK construction, see our Complete Guide to Construction Supplier Prequalification.

Sources and References

  • Common Assessment Standard — question set, recognised assessment bodies, certification levels, and the PPN 03/24 position — Build UK
  • PPN 03/24, Standard Selection Questionnaire (2024 update) — Cabinet Office (PDF)
  • CHAS membership packages (tier scope and starting prices) — chas.co.uk
  • Constructionline subcontractor memberships (level descriptions and CAS mapping) — constructionline.co.uk
  • SSIP Core Criteria (the 16 assessment elements) — ssip.org.uk
  • SSIP Core Criteria for the demonstration of organisational capability — "all member schemes undertake an assessment based upon the SSIP Core Critieria which is the threshold standard" (SSIP's own spelling); also the source for the CAS scope limit ("does not currently include an assessment against the Building Safety Act or other elements of the Common Assessment Standard [CAS] such as Environmental, Equality, Modern Slavery or Anti-Bribery") and the Section 4 exemption ("Common Assessment Standard: Section 4: Health & Safety (questions 135-173)") — ssip.org.uk
  • SSIP member register (Registered Member vs Supporter Member categories) — ssip.org.uk
  • Building Act 1984, section 120D — definition of "higher-risk building" ("at least 18 metres in height or has at least 7 storeys") — legislation.gov.uk
  • The Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023 (SI 2023/275), regulation 2 — specified descriptions — legislation.gov.uk
  • SI 2026/20, regulations 1(2) and 3(1) — Building Safety Regulator established as a body corporate from 27 January 2026 — legislation.gov.uk

Disclaimer: This guide is based on publicly available information including published Procurement Policy Notes, legislation, and industry guidance. Scheme tier names, prices and CAS mappings were verified September 2026. TenderReady is not affiliated with, endorsed by, or acting on behalf of SSIP, CHAS, Constructionline, the Cabinet Office, the HSE, or any other named body or scheme. Regulatory requirements and accreditation criteria are subject to change — always verify current details with the relevant organisation directly.