Summary
To get Common Assessment Standard (CAS) certified, you apply to one of the seven Build UK Recognised Assessment Bodies - such as Constructionline, CHAS or Compliance Chain - complete the industry-agreed question set, submit supporting evidence and pass either a desktop or site-based audit. Certification lasts one year. Because of CAS data sharing, you only need to be certified once and can then share the result with other bodies and clients. This guide walks through the process step by step, explains the two audit levels, and shows how to prepare so you pass first time.
What CAS Certification Actually Proves
CAS certification tells buyers and main contractors that an independent Recognised Assessment Body has checked your company against the Common Assessment Standard question set and confirmed you meet the required criteria across areas including health and safety, financial standing, building safety, environmental and quality management.
For suppliers, the real prize is access to work: many principal contractors and public sector buyers now require CAS as a condition of bidding. New to the standard itself? Start with our pillar guide which includes a free downloadable checklist, What is the Common Assessment Standard?
Step 1: Choose a Recognised Assessment Body
CAS certification can only be issued by a Build UK Recognised Assessment Body (RAB). There are seven, including Constructionline (the founding body, through which most suppliers certify via its Gold membership), CHAS and Compliance Chain. The full, current list is maintained on the Build UK website.
Because of the CAS data-sharing agreement, the body you choose does not limit who can see your certification - you certify once and share with any other RAB or client. So choose based on cost, the audit experience, the support offered and whether your key clients have a preferred body.
Step 2: Decide Which Audit Level You Need
CAS has two certification levels. Which one applies depends on your trade, size and what your clients require.
Audit level | What happens | Typically suits |
Desktop | The assessment body verifies your question-set answers and evidence remotely. | Most suppliers; lower-risk trades; smaller businesses. |
Site-based | An auditor visits your premises or a site to verify that your policies are implemented in practice. | Higher-risk trades, larger contractors, or where a client specifically requires it. |
Micro-businesses are assessed proportionately, so the requirements scale to the size of your organisation.
Step 3: Complete the Question Set
You then work through the CAS question set, which is divided into 10 sections covering identity, financial information, business and professional standing, health and safety, building safety, environmental management, quality, equal opportunities, business ethics and information management.
Most questions are mandatory, and many require supporting documents as evidence - not just a yes/no answer. Our Common Assessment Standard checklist breaks down each section and the evidence you will need to provide.
Step 4: Gather Your Evidence
This is where most applications slow down. Typical evidence includes:
- Health & safety policy and arrangements (or a valid SSIP certificate, which can satisfy much of this section)
- Two years of accounts or equivalent financial information
- Insurance certificates (with the company name matching your registered name exactly)
- ISO 9001 and ISO 14001 certificates where held - and you should know how to validate ISO certifications
- Environmental, quality, equality and modern slavery policies
- Evidence for the mandatory Building Safety section if you carry out work under the Building Safety Act
A common, avoidable failure point is mismatched or expired documents. Keeping certificates and policies current and consistently named throughout the year removes most of the friction.
Step 5: Submit and Be Audited
Once submitted, your Recognised Assessment Body reviews your answers and evidence against the assessment criteria. For a desktop audit this is done remotely; for a site-based audit an auditor will also visit to confirm your arrangements are actually in place. A successful audit results in CAS certification.
Step 6: Maintain and Renew Annually
CAS certification is valid for one year. Renewal is far easier when documentation has been kept up to date in the meantime - rather than scrambling to rebuild evidence each cycle. Remember too that standard updates can force an early refresh: when Version 5 made the Building Safety section mandatory, many suppliers had to update their assessment ahead of their normal renewal date.
How Long Does It Take?
Timelines vary by body and by how prepared you are. The single biggest factor is evidence readiness: suppliers with current, well-organised documentation can move through the process quickly, while those starting from scratch on policies and certificates take considerably longer. Preparing your evidence before you start the question set is the fastest route.
How to Pass First Time
- Audit your own documents first. Check every policy, certificate and insurance document is current and consistently named.
- Map your existing accreditations. A valid SSIP certificate or ISO certifications can exempt you from or shortcut parts of the question set.
- Prepare the Building Safety section early if you do design or building work under the Building Safety Act - it is now mandatory.
- Centralise everything. Storing compliance documents in one managed system makes both the initial audit and annual renewal dramatically easier.
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.
What Is the Common Assessment Standard (CAS)? A Complete Guide
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.