Understanding the differences between PAS 91, SSIP, and the Common Assessment Standard (CAS) can be confusing. Each serves a distinct purpose in the construction prequalification process, and knowing which one applies to your business is essential when bidding for contracts and demonstrating compliance.
This guide explains what each assessment covers, when you need them, and how they fit together within todays’ procurement landscape.
What is PAS 91?
PAS 91 was a standardised prequalification questionnaire (PQQ) system developed by the British Standards Institution (BSI) It provided a universal framework for assessing contractor capability across key areas of risk management.
In April 2023 PAS 91 was formally withdrawn by BSI and is no longer maintained or supported as an active standard.
What replaced PAS91?
The Common Assessment Standard (CAS) has superseded PAS 91as the industry recognised pre-qualification framework in construction. CAS builds on the structure of PAS 91 while expanding its scope to reflect evolving regulatory and compliance requirements, including those introduced by the Building Safety Act.
You can learn more about the Common Assessment Standard (CAS) as the current replacement standard later in this guide.
In addition, Cabinet office Procurement Policy Notice (PPN) 03/24 confirms public sector contracting authorities should use the Common Assessment Standard for construction works procurement. As a result, PAS 91 is no longer appropriate for public sector construction prequalification. While some private sector clients may still reference elements of the legacy PAS 91 framework, organisations are strongly encouraged to transition to CAS to align with current industry expectations.
The Common Assessment Standard: A CHAS Guide for Easy Completion
Read our guide to find out more about:
– Benefits of getting certified against the Common Assessment Standard
– The modules and different areas of risk management covered
– How to become certified against the Common Assessment Standard with CHAS Elite
By submitting this form you confirm you are happy to be contacted by CHAS in accordance with our Privacy Policy
What did PAS 91 cover?
The PAS 91 modules covered five core areas of risk management:
- Health and Safety
- Environmental Impact and Sustainability
- Quality Management
- Financial and Business Standing
- Equality, Diversity and Inclusion (EDI)
One of the key benefits if PAS 91 was standardisation, enabling contractors to complete a single structured questionnaire rather than responding to multiple bespoke PQQs for different clients.
When do you need PAS 91?
PAS 91 is no longer in use for public sector contracts, following its formal withdrawal by the British Standards Institution (BSI) in April 2023.
Although some private clients may still refer to legacy PAS 91-style questionnaires, it is no longer an active standard. Contractors seeking to demonstrate up-to-date compliance should instead pursue the Common Assessment Standard.
What is SSIP?
SSIP stands for Safety Schemes in Procurement. Unlike the now withdrawn PAS 91 or CAS, SSIP is not an assessment itself. It’s an umbrella forum that coordinates multiple health and safety assessment schemes under a mutual recognition framework, allowing contractors to demonstrate competence without duplicating assessments.
SSIP schemes access contractors against core health and safety criteria aligned with guidance from the Health and Safety Executive (HSE). If you achieve SSIP certification through one SSIP member scheme, like CHAS (a founding SSIP member), that certification is recognised by other SSIP members, helping to avoid duplication.
What does SSIP assessment involve?
To achieve SSIP certification with CHAS, you need to complete two modules:
- Health and Safety Assessment
- Insurance Verification
Your SSIP certificate demonstrates that you’ve met recognised health and safety standards, and one certified, contractors are listed on the SSIP portal, making it easier to share your credentials with clients.
When do you need SSIP?
SSIP certification is essential if you’re tendering for contracts where clients specify SSIP membership as a requirement.
Many construction clients use SSIP as a baseline demonstration of health and safety competence, particularly for subcontractor approval and supply chain compliance.
What is the Common Assessment Standard (CAS)?
The Common Assessment Standard (CAS) is the most comprehensive construction prequalification assessment currently available.
Developed by Build UK, in collaboration with the Civil Engineering Contractors Association (CECA), and industry experts, CAS expands on the original PAS 91 framework.
CAS covers 13 key areas of risk management:
- Identity
- Financial
- Insurance
- Corporate and Professional Standing
- Health and Safety
- Environmental
- Quality
- Equality, Diversity and Inclusion (EDI)
- Corporate Social Responsibility (CSR)
- Information Security
- Information Management
- Anti-Bribery and Corruption
- Modern Slavery
CAS is widely recognised as the industry benchmark for construction prequalification.
When do you need CAS?
Following the release of Procurement Policy Note (PPN) 03/24, central government departments and in-scope public sector bodies are required to adopt the Common Assessment Standard for construction works procurement.
Implementation deadlines introduced during 2024 mean CAS certification is increasingly essential for contractors seeking public sector work.
CAS is also becoming more common within the private sector, particularly among clients seeking a comprehensive, standardised approach to supply chain risk management.
PAS 91 vs SSIP vs CAS: key differences
Understanding how these three assessments differ helps you determine which one (or combination) your business needs.
Scope of assessment
- PAS 91 focuses on five core areas of risk management and has now been withdrawn.
- SSIP primarily addresses health and safety competence. CAS offers the most comprehensive coverage, addressing 13 areas of risk management and representing the highest standard of prequalification in the industry.
Regulatory status
PAS 91 was withdrawn in April 2023 and is no longer supported.
SSIP remains widely recognised as a health and safety assessment route.
CAS is required for in-scope public sector construction procurement under PPN 03/24.
Depth of compliance
SSIP demonstrates health and safety competence.
CAS demonstrates full-spectrum organisational compliance across financial, governance, ethical and operational risk areas.
How do PAS91, SSIP and CAS work together?
Although PAS 91, SSIP and the Common Assessment Standard serve different purposes, they are interconnected within the broader construction prequalification landscape.
- SSIP focuses specifically on health and safety competence.
- PAS 91 (now withdrawn) provided a structured PQQ framework across five risk areas.
- CAS builds on that structure and expands it into a comprehensive 13-area assessment covering financial, governance, ethical and operational compliance.
In practice, contractors are often required to demonstrate compliance at multiple levels. A client may require SSIP certification as a baseline for health and safety, while also requesting broader organisational assurance through CAS.
Rather than treating these as separate, standalone exercises, many assessment providers structure their services to streamline the process — allowing contractors to meet multiple requirements through a single route.
Free Contractors Compliance Checklist
This useful health and safety tool is a quick and easy way to help ensure all contractors arriving on-site have their compliance status checked.
Enter your details, and we’ll email you a free checklist that’s ready to use.
By submitting this form you confirm you are happy to be contacted by CHAS in accordance with our Privacy Policy
How CHAS structures its assessments
CHAS aligns its membership levels to reflect these different compliance needs:
- CHAS Standard provides SSIP certification.
- CHAS Advanced enable contractors to meet SSIP requirements while also addressing legacy PAS 91 requirements
- CHAS Elite delivers certification against the Common Assessment Standard, which includes SSIP compliance and covering all 13 risk management areas in accordance with the most up-to-date industry standards.
This tiered structure enables contractors to scale their certification in line with client expectations, without duplicating effort across multiple schemes.
Which assessment do you need?
The assessment you need depends on your target clients and contract types:
Choose CHAS Standard if:
- You need recognised health and safety certification.
- You’re working with clients who only require SSIP membership.
- You want an affordable entry-level compliance assessment.
Choose CHAS Advanced if:
- You need SSIP certification plus broader prequalification coverage.
- You work with private clients who still reference legacy PAS 91-style frameworks.
- You want to demonstrate compliance across 10 risk management areas.
Choose CHAS Elite if:
- You’re bidding for public sector contracts that require CAS.
- You want to meet the industry benchmark for prequalification.
- You need comprehensive compliance across all 13 risk management areas.
How CHAS Simplifies the assessment process
CHAS is a founding member of SSIP and was a recognised assessment body for both the withdrawn PAS 91 framework and what is now the current Common Assessment Standard. When you became a CHAS member, you could:
- Complete a single prequalification questionnaire to meet multiple requirements.
- Access expert guidance and support throughout the assessment process.
- Get listed on the CHAS client portal, connecting you with over 2,500 potential clients.
- Benefit from automatic prequalification for relevant projects.
- Maintain compliance with real-time alerts when certificates expire.
CHAS also offers CHAS Assist, a support package that provides:
- Assessment turnaround in as little as two working days.
- Dedicated one-to-one support from health and safety experts.
- Access to templates, documents and guidance.
- Award-winning customer service.
Start your assessment journey
Whether you require SSIP certification, need to satisfy private sector prequalification requirements, or are bidding for public sector contracts under the Common Assessment Standard, selecting the right level of assessment is essential.
By understanding the differences between PAS 91, SSIP and CAS, you can streamline your prequalification process, strengthen compliance, and improve your chances of winning work.
Ready to get started? Contact CHAS today to discuss which assessment package is right for your business.
