The Common Assessment Standard, Explained for Contractors

For years, construction suppliers filled in a different pre-qualification questionnaire for every client and every contractor they worked with: health and safety, insurance, quality, environmental policies, the same evidence in a dozen formats.

The Common Assessment Standard (CAS) was built by Build UK, the industry body, to end that. It is a single, industry-agreed question set with assessment standards behind it. You are audited against it once a year by an approved body, and clients accept the result.

It now sits at the centre of construction pre-qualification, including in public tenders. This is what a contractor or specialist trade actually needs to know about it.

What it replaced, and why it matters in public tenders#

The CAS question set includes, in Build UK's words, “all the key questions from the standard Selection Questionnaire (SQ) and the now withdrawn PAS 91”. If a contractor is still asking you for PAS 91, the standard they mean has been withdrawn, and the CAS now does its job.

In the public sector, government policy points to the CAS for works. Build UK's overview for public sector clients quotes PPN 03/24: for works contracts, including mixed contracts, authorities “should use the Common Assessment Standard in place of the standard SQ template”. The government's Procurement Specific Questionnaire template says the same for procurements under the Procurement Act 2023.

The practical effect, from that same overview: a supplier holding CAS certification from a Recognised Assessment Body “is deemed to meet the requirements for stage 1 pre-qualification”. The buyer can then concentrate on questions specific to the project, “including whether the supplier meets any financial stability and insurance requirements”.

Two consequences follow:

• Certification does not finish the job. The project-specific questions, including the insurance levels for that contract, still have to be answered and checked.
• No certification is not automatically a barrier. The overview says a buyer can instead ask you to answer the relevant CAS questions directly and assess them itself.

Desktop or site-based?#

There are two levels of certification:

• Desktop: your answers and documents are assessed against the standard.
• Site-based: adds an audit that goes beyond the paperwork. The question set notes that companies undergoing a site-based audit “will be required to demonstrate how they implement” the policies and procedures their certifications cover.

Build UK says companies should choose the level “most appropriate for their business based on a range of factors including trade, size and the requirements of their clients”. In practice, the deciding factor is usually what your clients and main contractors ask for. Check their pre-qualification requirements before choosing.

Constructionline Gold, CHAS Elite and the rest#

Much of the confusion around the CAS comes from naming. You don't buy “the CAS”. You buy a scheme from one of the Recognised Assessment Bodies, and some of their schemes are CAS certification at one level or the other.

Build UK's current list maps them like this:

So “CHAS or Constructionline?” is often the wrong question. If the requirement is the Common Assessment Standard, the CAS-level schemes from different bodies are meant to be interchangeable. Build UK says certification is accepted by a growing list of contractors and clients “who no longer specify a particular assessment body”. If a tender names one scheme and nothing else, that is worth a clarification question.

Certified companies can also share their data with other Recognised Assessment Bodies, so it is visible to clients who use a different one.

What the question set covers#

The current question set, Version 6, is dated 1 November 2026. It has ten sections:

1. Identity
2. Financial
3. Corporate and professional standing
4. Health and safety
5. Environmental
6. Quality
7. Building safety
8. Fairness, inclusion and respect
9. Information security
10. Information management

Three details make it more manageable than it looks:

• Most questions are mandatory, some are advisory. You do not need the advisory ones to achieve certification, but Build UK notes that any not completed successfully “may be flagged” when your data is shared with clients.
• Exemptions. You may be exempt from some questions if you hold other third-party certifications such as ISO standards, or if a question doesn't apply to your business. For example, you may not use sub-contractors.
• Proportionality for micro-businesses. For companies that meet the micro-business criteria, the assessment standards are applied proportionately.

The building safety section matters beyond tendering. Build UK says it means the CAS can be used to show organisational capability for your role under the Building Safety Act.

The fifteen items that can quietly lapse#

Certification is valid for a year “provided that any ‘time critical’ documents are updated when they expire”. Build UK lists fifteen time-critical questions. In Version 6 they are:

Every one of these has its own renewal date, set by somebody else: an insurer, a certification body, an assessor. An insurance policy or certificate that was current at your annual assessment can expire a few months later, and a tender response that relies on it will be out of date too.

That makes the time-critical list the most practical part of the whole standard. Put every renewal date in one calendar, chase renewals before they lapse, and update your assessment body when new documents arrive. These are the same items that hold up tender submissions when they are left to the last week.

In short, for a contractor#

1. Find out what your clients ask for, desktop or site-based, before choosing a level.
2. Treat the scheme names as packaging. Check that the scheme you buy is a CAS level, and that the requirement accepts any Recognised Assessment Body.
3. Diarise the fifteen time-critical items. They decide whether your certificate is really current.
4. Remember the tender still asks project-specific questions, especially on insurance and financial standing. The certificate gets you through stage 1, not the whole selection.