Common Assessment Standard evidence for micro-businesses

A small construction supplier can find a Common Assessment Standard (CAS) questionnaire written for a much larger organisation. Build UK says its assessment standards are applied proportionately to micro-businesses. That does not mean a micro-business automatically passes, can mark every question “not applicable”, or is exempt from work-specific safety duties.

This guide is for a supplier preparing the current Version 5 evidence for a recognised assessment body. It focuses on how to decide what to supply, explain genuine exemptions and avoid producing impressive but irrelevant paperwork. The general CAS overview covers the whole standard and its desktop and site-based levels.

Establish which business is being assessed

Start with the legal form, registered or trading name, actual number of workers, subcontracting arrangements, declared trades and intended dutyholder roles. Give these facts to the recognised assessment body. Some conditional CAS answers depend on whether the company employs people, subcontracts, supplies products, operates vehicles or carries out design work. A micro-business with two employees and regular subcontractors cannot use the same answers as a sole trader who works alone.

Build UK links its micro-business criterion from the CAS overview. Check the current criterion and the assessment body's instructions rather than assuming that “small” in everyday language qualifies. Ask the assessor to resolve an uncertain classification before preparing a full evidence pack.

Use the N/A route question by question

The Version 5 question set identifies particular advisory items and conditional exemptions. Read the instruction attached to each question. Record the reason for an N/A answer and the fact that makes it true: for example, no employees, no supply of products, or no work in a specified dutyholder role. Where the question asks for alternative evidence, an N/A tick is not a substitute.

Do not copy another firm's N/A pattern. A buyer or assessor needs the response for your legal entity, work and risk. If an activity starts later, reassess the answer; the prior N/A may no longer fit.

Prepare the financial record that fits your legal form

Version 5 question 27 asks for accounts and gives different evidence routes for small companies, audited entities, unincorporated businesses and start-ups. A sole trader without company accounts should not upload a company's accounts belonging to someone else. The question set explains when relevant tax-return pages and a tax assessment may be used. A start-up without reported accounts has a separate forecast and funding route. Read the current wording and ask the assessor how to handle missing or confidential records.

The same principle applies to insurance. Version 5 question 28 allows N/A for employers' liability evidence where the company has no employees. That specific assessment answer is not a universal conclusion that an insurance obligation can never arise if the business changes how it works. Check the current GOV.UK employers' liability guidance for the actual legal position, and check each buyer's contractual cover requirement separately.

Show a working control, even if one person owns it

Proportionate evidence can be concise. A small supplier may use a clear procedure, a dated example and a named person to show how it assesses a hazard, briefs a worker, checks a subcontractor or reviews an incident. A copied policy that nobody uses is weaker than a short record that accurately reflects the work. HSE's small-builder guidance likewise frames planning effort around complexity and risk.

However, proportionate is not permission to omit a mandatory answer. Build UK's 23 July 2026 Building Safety statement says that until Version 6 is published, all suppliers undergoing CAS certification must successfully complete competence questions 135, 136 and 138, even where they do not need to answer the remaining dutyholder questions in that section. This current transition rule is particularly important for small scaffolding and temporary-works suppliers. Recheck it when the new standard takes effect.

Make an evidence index before uploading

For every applicable question, record the answer owner, source document or real example, date, version, confidentiality limit, assessor comment and final accepted response. For a conditional N/A, record the reason and the person who checked it. Keep the original evidence available; a spreadsheet summary alone may not satisfy an assessor who needs to inspect a document.

If a buyer asks for more than the CAS assessment requires, separate the buyer-specific request from the standard assessment. A CAS certificate does not establish that your team, equipment and method are suitable for every site or package. Ask for clarification when a tender's wording mixes CAS, SSIP and site-specific competence.

Teams handling multiple suppliers can review contractor prequalification software and ask for a demonstration of how it records entity, evidence owner, conditional answer and renewal date. Complys does not decide micro-business eligibility, apply exemptions, issue CAS certification or replace the recognised assessment body.

Primary sources and publication gate

• Build UK — CAS overview: proportional micro-business assessment, current Version 5 and scheduled Version 6.
• Build UK — CAS Version 5 question set: question-specific exemptions, question 27 accounts and question 28 employers' liability evidence.
• Build UK — 23 July 2026 Building Safety statement: temporary universal completion rule for questions 135, 136 and 138.
• HSE — small builders: proportionate planning and contractor safety duties.
• GOV.UK — employers' liability insurance: actual Great Britain legal insurance position.

Before publication: Verify the current Build UK version and whole live CAS overview. If the existing overview already serves the micro-business task in sufficient depth, merge this material into that owner instead of creating a second generic CAS result.