One is a UK pre-qualification accreditation that gets you onto tender lists. The other is an internationally certifiable management system. They overlap, they're often confused, and main contractors increasingly ask about both. Here is the honest difference.
If you run a contracting business in the UK, two health-and-safety credentials come up over and over: CHAS and ISO 45001. They sound like alternatives — pick one, tick the box — but they are different kinds of thing, doing different jobs. Confusing them leads to one of two mistakes: paying for a management-system certification you didn't need to win the work, or chasing a pre-qualification badge that doesn't satisfy a client who actually wanted a certified system. This piece sets out what each one is, where they genuinely differ, and the honest answer to "do I need both?"
CHAS stands for the Contractors Health and Safety Assessment Scheme. It is one of the UK's best-known SSIP accreditations. SSIP — Safety Schemes in Procurement — is an umbrella body that lets member assessment schemes recognise each other's certificates, so that a contractor assessed by one scheme doesn't have to be re-assessed from scratch by every client using a different one.
In practical terms, CHAS is a pre-qualification assessment. A contractor submits its health-and-safety arrangements — policy, risk assessments, method statements, training records, insurance, accident history — and an assessor checks them against the scheme's criteria, which align with the relevant parts of the published industry pre-qualification standard. Pass, and you get a CHAS accreditation that buyers recognise, often as a condition of being allowed to tender or appear on an approved-contractor list. CHAS membership also feeds into Constructionline, the widely-used UK supplier pre-qualification register, so the two frequently travel together in construction procurement.
A UK supply-chain pre-qualification accreditation that verifies your health-and-safety arrangements meet a recognised baseline — the credential that gets you past the gate and onto construction tender lists.
ISO 45001 is the international standard for an occupational health and safety management system. It is not a pre-qualification badge — it is a framework for how your organisation manages H&S, built on the same Annex SL structure (clauses 4 to 10) shared across ISO 9001, ISO 14001 and ISO 27001. It requires you to understand your context and interested parties, demonstrate leadership and worker participation, plan around hazards and risks, control your operations, evaluate performance, and continually improve.
Crucially, ISO 45001 is certifiable by an accredited certification body. An external auditor assesses your management system against the standard, and — if it conforms and is effectively implemented — issues a certificate, then returns for surveillance audits to confirm you're keeping it up. A distinctive feature of 45001 compared with older H&S approaches is its strong emphasis on worker consultation and participation: the people exposed to the risks must have a genuine voice in the system that manages them.
A certifiable, internationally recognised management-system standard for occupational health and safety — proof you run a genuine, audited, continually-improving H&S system, not just that you hold the right paperwork.
Set side by side, the distinction becomes clear: CHAS verifies that your arrangements meet a baseline at a point in time; ISO 45001 certifies that you operate a living management system.
| CHAS | ISO 45001 | |
|---|---|---|
| What it is | SSIP pre-qualification accreditation for health & safety | Certifiable international management-system standard |
| Scope | Verifies H&S arrangements meet a recognised baseline | Whole H&S management system: context, leadership, planning, operation, evaluation, improvement |
| Recognition | UK supply chains, especially construction; mutual recognition across SSIP; feeds Constructionline | International; recognised by clients worldwide and across sectors |
| Audit depth | Document-led assessment against scheme criteria | On-site management-system audit by an accredited body, plus ongoing surveillance |
| Who asks for it | Principal contractors, public-sector buyers, framework operators as a tender condition | Larger clients and tenders that require a certified, audited H&S system |
| Renewal | Periodic re-assessment (typically annual) | Three-year certification cycle with annual surveillance audits |
A useful way to hold the two in mind: CHAS checks your paperwork against a standard; ISO 45001 certifies the system that produces the paperwork. CHAS is broadly easier and quicker to achieve, and is the more common explicit requirement on UK construction tenders. ISO 45001 is the deeper commitment — a system, not a submission — and carries international weight.
For a lot of UK contractors, the honest answer is often yes — but for different reasons.
You'll typically want CHAS (and the Constructionline registration that usually rides with it) because it is the credential principal contractors and public-sector buyers explicitly ask for at pre-qualification. Without it, you may simply not be allowed to tender for a large share of construction work. It is, bluntly, a commercial gateway.
You'll want ISO 45001 when clients require a certified management system, when you want international credibility, or when you genuinely want a managed, continually-improving approach to safety rather than a once-a-year evidence scramble. For higher-value, higher-risk or framework work, a 45001 certificate increasingly carries weight.
The two reinforce each other. Running an ISO 45001-style system is the single best way to make CHAS easy: the policy, risk assessments, method statements, training records, accident data and management review that 45001 requires you to maintain continuously are exactly the evidence CHAS assessors want to see. Build the system once, and the accreditation becomes a by-product rather than a project. Many contractors quite reasonably sequence it that way — establish a 45001-style system, use it to sail through CHAS to win the work, then pursue formal 45001 certification when a client or growth ambition calls for it.
The wrong move is to treat them as either/or. CHAS without an underlying system is fragile — you're rebuilding the submission from scratch every year. A 45001 certificate without CHAS may leave you locked out of construction tenders that demand the SSIP badge by name. For most contractors with construction exposure, both have a role.
What CHAS and ISO 45001 have in common is that both are won or lost on evidence — your H&S policy, risk assessments and method statements (RAMS), training and competence records, hazard register, accident and incident data, insurance, and the audit and review trail that shows the system is alive. The contractors who struggle aren't the ones with bad safety; they're the ones whose evidence is scattered across folders, inboxes and spreadsheets when an assessor or a client asks for it.
The PICMS SHEQ platform and its Construction pack are built for exactly this: hazard and risk registers, RAMS, training and competence tracking, incident records, and the audit and management-review trail kept in one place, with support for assembling CHAS / Constructionline pre-qualification evidence alongside an ISO 45001-aligned management system. The AI evidence-to-clause mapping shows you which documents you hold against each Annex SL requirement, so you can see the gaps before an assessor does.
To be plain about what software does and doesn't do: PICMS doesn't make you CHAS-accredited or ISO 45001-certified — those come from the assessor and the certification body. What it does is keep the evidence behind both complete, current and traceable, so demonstrating alignment is a matter of pulling it up rather than rebuilding it under deadline.
The PICMS Construction pack keeps your hazard register, RAMS, training records, incidents and audit trail in one place — supporting CHAS / Constructionline pre-qualification alongside an ISO 45001-aligned management system.