CAS desktop versus site-based assessment

The Common Assessment Standard (CAS) has desktop and site-based certification levels. They are not two different laws. They are assessment routes within the construction industry's prequalification standard. A supplier's useful question is which level a particular client accepts for the work it wants to bid for, and which recognised assessment body offers it.

Build UK's current CAS overview says companies apply to a recognised assessment body for the level appropriate to their trade, size and client requirements. Its table names the provider products that correspond to desktop or site-based certification. Do not infer the CAS level from a provider's brand name, the colour of a membership badge or an older sales brochure.

What each level tells a buyer

A desktop assessment reviews a supplier against the relevant CAS question set without the site-based audit that forms the other level. Site-based certification adds that audit route. The exact assessment method and product name are administered by the recognised body, so ask it for its current assessment scope rather than relying on a generic comparison table.

Neither level alone proves that a named crew is competent for a particular task or that a method statement suits the buyer's site. HSE's guidance on conformity assessment schemes says third-party assessment is one route to prequalification, but a buyer still needs to check project-specific skills, track record and site requirements. A site-based CAS product is not a blanket authorisation for every future site.

Decide in four steps

1. Read the actual tender or framework condition. Identify the named standard, required level, legal entity, expiry date and any accepted equivalent route. A client's procurement policy may be more specific than a general statement that it “accepts CAS”.
2. Check the recognised-body table. Build UK's CAS page lists current products under each level. Some bodies offer both; others list only desktop. Confirm that the proposed product is the one associated with the required level.
3. Describe your actual role and work. Tell the assessment body whether the applicant designs, manages, installs, maintains or subcontracts the work, and whether it is taking a principal dutyholder role. The appropriate evidence follows the scope of the business, not a marketing tier.
4. Confirm what the buyer can see. Build UK's data-sharing overview explains that specified verified CAS data can be shared across recognised bodies following the supplier's request and consent. It does not transfer the underlying documents and certificates automatically. If a buyer asks for those, follow its secure submission instructions.

If the tender wording is ambiguous, ask the buyer before purchasing or upgrading a product: “Do you require desktop or site-based CAS certification, and will you accept an equivalent assessment?” Keep the answer with the tender record. A supplier already holding a current desktop product should not assume it satisfies a site-based condition, and a buyer should not demand the highest tier without a proportionate reason for the work.

Keep certification and mobilisation separate

For a supplier, CAS reduces repeated organisational prequalification. For a buyer, it is one input to selection. The buyer still needs to decide whether the supplier, named people, insurance, equipment and work method fit the particular package. Our buyer verification guide covers that later decision; the general CAS explainer covers the standard itself.

When evaluating contractor prequalification software, ask the vendor to demonstrate how the legal entity, recognised assessment body, product, level, expiry and buyer-specific decision are recorded. This article does not claim Complys certifies CAS, upgrades supplier membership or verifies a third-party portal automatically.

Primary sources and integration gate

• Build UK — Common Assessment Standard: the two levels and current recognised-body product table.
• Build UK — Data Sharing: limited shared data and supplier permission, without underlying document transfer.
• HSE — Health and safety conformity assessment schemes: assessment is one prequalification route, not proof of site-specific risk management.

Before integration: Compare the whole live CAS overview and provider comparison content. If either has become a complete desktop-versus-site-based decision guide, merge this material into that owner. Recheck Build UK's current product table and CAS version if publication occurs after Version 6 begins.