SMAS vs CHAS – What's the Difference for UK Contractors?
A factual overview of SMAS and CHAS, how both operate within the SSIP framework, and how independent ISO 17021 certification compares for UK contractors.
Overview: SMAS and CHAS
SMAS – Safety Management Advisory Service
SMAS is a health and safety prequalification scheme and SSIP member operating across the UK. It assesses contractors' health and safety management systems and documentation, providing a certificate accepted by a wide range of buyers. SMAS offers a tiered approach with options including Worksafe, Contractor Plus and PAS 91 assessments. Annual renewal is required to maintain status.
- SSIP member scheme
- Health & safety focused
- Annual membership renewal
- Buyer verification portal
- Tiered product options
CHAS – Contractors Health and Safety Assessment Scheme
CHAS is one of the most established UK prequalification schemes, operating since 1997. It is widely accepted in the public sector, housing and construction supply chains. CHAS assesses health and safety competence documentation and provides a buyer-facing verification portal. Like SMAS, it is an SSIP member and requires annual renewal.
- SSIP member scheme
- Established since 1997
- Public sector widely accepted
- Annual membership renewal
- Buyer verification portal
Understanding the SSIP Framework
SSIP (Safety Schemes in Procurement) is a UK forum that promotes mutual recognition between health and safety prequalification schemes. Achieving assessment through any SSIP member scheme means most SSIP-accepting buyers will recognise your status, avoiding the need for duplicate assessments with multiple providers.
Both SMAS and CHAS are SSIP members. From a practical procurement perspective, this means that for buyers who accept any SSIP scheme, there is no substantive difference in the prequalification outcome. The choice between SMAS and CHAS for many contractors therefore comes down to:
- Which specific buyers require each scheme by name
- Pricing and renewal cost comparison
- Additional services or products included in membership
- Existing relationships or historical status with a provider
- Scope of optional assessments (e.g. CDM Advisor, PAS 91)
Assessment Structure: SMAS vs CHAS vs NAS
| Aspect | SMAS | CHAS | NAS (ISO 17021 model) |
|---|---|---|---|
| Scheme Type | SSIP prequalification membership | SSIP prequalification membership | Independent certification body |
| Assessment Scope | Health & safety management | Health & safety management | Compliance, governance, operational standards |
| ISO Alignment | SSIP framework, not ISO 17021 | SSIP framework, not ISO 17021 | ISO 17021 aligned model |
| Assessment Model | Internal document review by SMAS team | Internal document review by CHAS team | Independent assessor + separate decision manager |
| Certificate Issued | SMAS certificate of membership | CHAS certificate of membership | Formal NAS certification (Basic/Silver/Gold) |
| Renewal Cycle | Annual renewal | Annual renewal | Surveillance/recertification cycle |
| SSIP Mutual Recognition | Yes | Yes | Independent body – not SSIP member |
| Pricing Model | Annual membership fee | Annual membership fee | Published one-time certification fee (£749–£1,150) |
Information based on publicly available descriptions. Verify directly with each provider for current details.
How NAS Fits Alongside SMAS and CHAS
NAS does not replace SMAS or CHAS for buyers who specifically require SSIP prequalification. Rather, NAS operates as a complementary independent certification body for organisations that need formal, ISO 17021 aligned certification covering a broader scope of compliance and governance.
Many contractors and SMEs find value in maintaining SSIP prequalification alongside independent certification, as these serve different buyer segments and demonstrate different aspects of organisational competence.
For organisations operating or seeking work in the USA as well as the UK, NAS's sister operation NRTAUS provides equivalent independent certification in the American market.