Summary
The Common Assessment Standard (CAS) is the UK construction industry's standardised pre-qualification questionnaire (PQQ), developed by Build UK. It replaced PAS 91 - which was withdrawn by BSI in April 2023 and is now the preferred pre-qualification method for public sector construction procurement under Procurement Policy Note PPN 03/24. CAS uses a single industry-agreed question set, divided into 10 sections, that lets a supplier prove their capability and compliance once and share it with multiple buyers. The current Version 5 (published 1 July 2025) made the Building Safety section mandatory. Around 21,000 suppliers now hold CAS certification through one of seven Recognised Assessment Bodies.
What Is the Common Assessment Standard?
The Common Assessment Standard is a unified pre-qualification framework for the construction industry. It combines an industry-agreed question set with corresponding assessment criteria, so that a supplier's competence and compliance can be assessed once and recognised by many different clients and main contractors.
The aim is simple: end the duplication that has always plagued construction pre-qualification. Before a single standard existed, a subcontractor might complete a dozen near-identical questionnaires a year, each in a slightly different format. CAS lets a supplier complete one assessment, be certified by a Recognised Assessment Body and have that certification accepted across the public and private sectors.
For buyers and main contractors, CAS provides confidence that a supplier has been independently assessed against a consistent, modern set of risk-management criteria - covering everything from health and safety and financial standing to building safety and information management.
Who Developed CAS, and When?
CAS was developed by Build UK together with the Civil Engineering Contractors Association (CECA) and other accreditation bodies and industry experts. It was launched in 2019, with CHAS becoming the first body to offer the scheme.
A pivotal moment came in 2021, when a data-sharing agreement was introduced between the assessment bodies. This meant a supplier only had to be certified once: the result could then be shared with any other Recognised Assessment Body, removing the need to repeat the process. That single change accelerated adoption significantly, and today more than 21,000 suppliers hold CAS certification.
How CAS Replaced PAS 91
CAS is the successor to PAS 91, the BSI pre-qualification questionnaire that served the industry from 2010. PAS 91 was formally withdrawn by the British Standards Institution in April 2023 and is no longer maintained or updated.
The shift was driven by the Building Safety Act 2022 and a wider recognition that procurement needed a more comprehensive, regularly updated framework. CAS keeps the core areas PAS 91 covered but extends them - adding building safety, information management, modern slavery and broader governance requirements.
If you are weighing up the two frameworks directly, our guide to PAS 91 vs the Common Assessment Standard sets out the differences side by side.
The 10 Sections of the CAS Question Set
The CAS question set is divided into 10 sections, each covering a specific area of compliance and risk management. Splitting the questionnaire this way lets suppliers work through it in manageable parts, and lets buyers see clearly which risk areas a supplier has been assessed against.
# | Section | What it covers |
1 | Identity | Core company information - registration, structure, business type and size. |
2 | Financial Information | Accounts, financial standing and stability over the last two years. |
3 | Business & Professional Standing | Convictions, sanctions and other matters affecting eligibility to bid. |
4 | Health & Safety | H&S policy, arrangements, competence and accident history. |
5 | Building Safety | Organisational capability to meet duties under the Building Safety Act. |
6 | Environmental Management | Environmental policy, ISO 14001 and waste-handling arrangements. |
7 | Quality Management | Quality control and assurance, including ISO 9001. |
8 | Equal Opportunities / Fairness, Inclusion & Respect | Equality, diversity and anti-discrimination policy and practice. |
9 | Business Ethics | Modern slavery, anti-bribery and corruption arrangements. |
10 | Information Management | How the organisation specifies, stores, secures and exploits project data (including BIM and common data environment capability). |
Most questions are mandatory, though suppliers may be exempt from some sections if they already hold a relevant accreditation - for example, a valid SSIP certificate can satisfy much of the Health & Safety section. The exact wording and question numbers are set out in Build UK's published Version 5 question set, which is the definitive reference. For a practical walk-through of what each section asks for, see our Common Assessment Standard checklist.
CAS Checklist
Our free CAS checklist provides a structured framework to help you build your PQQ in line with the Common Assessment Standard (CAS). Each section in the contents links directly to a corresponding tab, making it easy to navigate and use.
What Changed in Version 5 (July 2025)?
Build UK published Version 5 of the question set on 1 July 2025. The headline change is that the Building Safety section became mandatory. When it was first introduced in July 2024, completion was advisory for the first 12 months to give the industry time to adapt; from V5 it must be completed by every company carrying out design or building work that falls under the Building Safety Act.
Version 5 also updated the Corporate & Professional Standing, Environmental, and Fairness, Inclusion & Respect (FIR) sections to reflect new legislation and guidance. Crucially, many large contractors instructed their supply chains to complete the mandatory Building Safety questions by 1 October 2025 - which meant a significant number of suppliers needed an updated assessment well before their normal annual renewal.
The Building Safety section connects directly to the wider duty-holder regime and the principle of the Golden Thread of building information.
Who Needs the Common Assessment Standard?
CAS is relevant to two groups:
- Suppliers and subcontractors who want to win construction work. Holding CAS demonstrates capability and compliance to buyers, and thanks to data sharing, removes the need to complete multiple separate PQQs.
- Buyers, main contractors and public sector clients who need to pre-qualify their supply chain consistently and evidence that risk has been managed across it.
CAS applies across both the public and private sectors. In the public sector its use is now expected for larger contracts (see the next section). In the private sector, many of the UK's principal contractors require their subcontractors to hold CAS, including the Building Safety section, as a condition of working with them.
CAS and Public Sector Procurement (PPN 03/24)
In March 2024 the Government issued Procurement Policy Note PPN 03/24, directing public sector contracting authorities to use the Common Assessment Standard for construction works procurement. For public sector projects above the £5.337 million threshold, CAS is now the preferred pre-qualification method.
PPN 03/24 is guidance to public sector buyers rather than a statutory obligation on contractors, but its practical effect is clear: CAS compliance is increasingly a gate to public sector work, and adoption is widening. We cover this in detail in PPN 03/24 explained.
How CAS Relates to SSIP
It is easy to confuse CAS with SSIP (Safety Schemes in Procurement), but they are different in scope. SSIP is concerned only with health and safety competence - it provides mutual recognition between H&S assessment schemes so suppliers don't have to prove the same thing repeatedly. CAS is broader: it covers health and safety as one of its 10 sections, alongside financial, environmental, quality, building safety, ethics and information-management criteria.
The two interact: holding a valid SSIP certificate can exempt a supplier from much of the CAS Health & Safety section. For a full comparison, including how CHAS and Constructionline fit in, read Common Assessment Standard vs SSIP.
How to Get Certified
Certification is carried out by one of seven Build UK Recognised Assessment Bodies - including Constructionline, CHAS and Compliance Chain. There are two audit levels, desktop and site-based, and certification lasts one year before renewal. Most suppliers obtain CAS through Constructionline's Gold membership.
Our step-by-step guide to getting CAS certified covers choosing a body, the audit process, costs and how to prepare.
How Technology Helps You Manage CAS
Whether you are a supplier maintaining your own certification or a buyer mandating CAS across a supply chain, the administrative load is real: collecting evidence, tracking certificate and insurance expiries, and keeping documentation audit-ready all year round.
Mobilize by Liaison Systems automates supplier pre-qualification, stores compliance documentation in one place, tracks expiries automatically and gives buyers full visibility of supply chain compliance against standards like CAS - so suppliers stay tender-ready and buyers can evidence risk management with confidence.
Final Thoughts
The Common Assessment Standard is now the benchmark for construction pre-qualification in the UK. With PAS 91 withdrawn, the Building Safety section mandatory, and public sector procurement pointing firmly towards CAS, understanding the standard is essential for anyone bidding for or buying construction work. The good news is that CAS is designed to reduce duplication, not add to it - and with the right process and tools, staying compliant is straightforward.
If you need help managing CAS compliance across your supply chain, our team can help.
Posted on 25 May 2026
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Common Assessment Standard vs SSIP: What's the Difference?
The Common Assessment Standard (CAS) and SSIP (Safety Schemes in Procurement) are often confused, but they cover very different ground. SSIP deals only with health and safety competence and provides mutual recognition between H&S assessment schemes. CAS is far broader - a full pre-qualification framework covering 10 areas, of which health and safety is just one. CHAS and Constructionline are not standards at all; they are assessment bodies that can certify you against both SSIP and CAS. This guide explains how they relate, where they overlap, and which your business actually needs.
The Common Assessment Standard Checklist: All 10 Sections Explained
The Common Assessment Standard (CAS) question set is divided into 10 sections, each covering a different area of compliance and risk management. To pass your audit, you need the right evidence ready for each one - not just a yes/no answer. This checklist explains all 10 CAS sections, what each looks for, and the documents you should have to hand before you start. Use it to gap-check your own readiness, then download our free CAS checklist to track your progress section by section.
PPN 03/24 Explained: What It Means for Construction Pre-Qualification
Procurement Policy Note PPN 03/24 is UK Government guidance, issued in March 2024, that directs public sector contracting authorities to use the Common Assessment Standard (CAS) when pre-qualifying suppliers for construction works. For public sector projects above the £5.337 million threshold, CAS is now the preferred pre-qualification method, replacing PAS 91. PPN 03/24 is guidance to buyers rather than a law imposed on contractors - but in practice it means CAS compliance is increasingly a gate to public sector construction work. This guide explains what PPN 03/24 says, who it affects and what suppliers and buyers should do about it.