The Complete Guide to Construction Supplier Prequalification in the UK

If you run a construction business with 5 to 50 employees, you already know the score: before you can price a job, you need to prove you can do it safely and competently. That process — supplier prequalification — has become the gatekeeping mechanism of the UK construction industry. Understanding how it works, which schemes matter, and what assessors actually look for is the difference between a pipeline full of opportunities and being locked out of the supply chain.

This guide breaks down the prequalification process, from the major schemes and standards to practical steps for getting your business assessment-ready.

What Is Construction Supplier Prequalification?

Supplier prequalification is the process by which clients, principal contractors, and public-sector buyers verify that a contractor or subcontractor meets minimum standards before being invited to tender. In construction, this overwhelmingly focuses on health and safety management, but increasingly extends to environmental management, financial standing, equality, and modern slavery compliance.

For decades, prequalification was fragmented — every main contractor had their own questionnaire, and subcontractors would spend weeks filling in near-identical forms. The industry has since consolidated around a handful of recognised assessment schemes and a common framework, but the system remains confusing for many SMEs entering the supply chain for the first time.

The Common Assessment Standard (CAS) — and the PAS 91 It Replaced

Before looking at individual schemes, it is worth understanding the framework that underpins them.

The Common Assessment Standard (CAS)

The Common Assessment Standard is the framework that ties the major construction prequalification schemes together. Developed by Build UK in partnership with the SSIP schemes and Constructionline, CAS sets out a standardised set of assessment criteria — covering health and safety and a wider set of risk-management areas — that recognised assessment bodies certify contractors against.

The practical effect for contractors: CAS is now the industry-recognised prequalification framework. Build UK states that "Central Government departments and wider public sector bodies should use the Common Assessment Standard to pre-qualify suppliers in accordance with PPN 03/24". See our dedicated guide: The Common Assessment Standard (CAS) Explained.

PAS 91: The Withdrawn Predecessor

You may still see references to "PAS 91". PAS 91 was a Publicly Available Specification published by BSI (British Standards Institution) that provided a standardised format for construction prequalification questionnaires. BSI withdrew PAS 91 on 21 April 2023 — BSI's own catalogue record for PAS 91:2013+A1:2017 shows its status as "Withdrawn" with a withdrawal date of "21 Apr 2023", and PPN 03/24 says the same at paragraph 7, which records that the Selection Questionnaire "removed references to PAS91 which has now been withdrawn by the BSI" (verified 2 September 2026). It has been replaced by the Common Assessment Standard. If a procurer still asks for "PAS 91", they almost always mean current SSIP accreditation or CAS certification. See our full explainer: PAS 91 Is Withdrawn: What Replaced It.

How Mutual Recognition Works

Mutual recognition belongs to SSIP, not to CAS. SSIP sets the SSIP Core Criteria — the health and safety threshold standard its Registered Members assess against. The Common Assessment Standard is a separate, broader framework owned by Build UK, which describes it as "an industry-agreed question set and corresponding assessment standards for the pre-qualification of suppliers", certified at two levels: desktop and site-based. The two meet at one point: SSIP states that "any valid SSIP assessment completed by any of our member schemes and visible on the SSIP portal will provide exemption against Section 4 of the CAS" — Section 4 being the health and safety part of the CAS question set.

The practical effect for contractors: if you achieve accreditation through one SSIP member scheme, other SSIP members should recognise that assessment through a process called mutual recognition (sometimes referred to as "deem to satisfy"). This is designed to prevent contractors needing multiple, overlapping assessments.

In practice, mutual recognition works well for the core health and safety element, but it stops there. SSIP is explicit that the Core Criteria confirm "organisational capability against Health and Safety legislation" and that this "does not currently include an assessment against the Building Safety Act or other elements of the Common Assessment Standard [CAS] such as Environmental, Equality, Modern Slavery or Anti-Bribery". Those areas — plus financial standing and any sector-specific checks an individual scheme adds — require separate assessment.

The Major Prequalification Schemes

Four schemes dominate UK construction prequalification. Each operates slightly differently, serves different parts of the supply chain, and offers varying levels of assessment.

CHAS (Contractors Health and Safety Assessment Scheme)

CHAS is one of the most widely recognised health and safety assessment schemes in UK construction. Originally established by local authorities to standardise contractor vetting, it has grown into a national scheme used across both public and private sectors.

What it assesses: Health and safety policy, risk assessment competence, method statements, training arrangements, accident reporting, insurance, and management of subcontractors. The CHAS Elite tier extends into environmental management, quality management, financial assessment, anti-bribery, and modern slavery.

Who uses it: Local authorities, housing associations, facilities management companies, and an increasing number of Tier 1 and Tier 2 contractors. CHAS is often the first scheme that SME contractors encounter.

Tiers: CHAS publishes three contractor membership packages — Standard ("Meet SSIP requirements", from £429 a year), Advanced (adds "Meet the former PAS 91 standard", from £659) and Elite (adds "Meet Common Assessment Standard requirements", from £949).

SSIP member: Yes. Core health and safety assessment is mutually recognised by other SSIP members.

For a detailed walkthrough of the application process, see our guide: How to Get CHAS Accreditation: A Step-by-Step Guide for Contractors.

Constructionline

Constructionline is the UK's largest register of prequalified contractors and consultants for the construction industry. It states on its own about page that it "is part of the Once For All Group, European leaders in risk management, compliance, supply chain management & sourcing" — it is a commercial business, not a government body, though it is heavily used in public-sector procurement and by many Tier 1 contractors as a prequalification gateway.

What it assesses: Constructionline publishes five subcontractor membership levels — Associate, Bronze, Silver, Gold and Platinum. Associate is an entry to the platform; Bronze lets you "manage your insurance and SSIP data through a simplified question set"; Silver lets you "share your compliance and SSIP data with the largest construction and FM buyers"; Gold is "all the benefits of Silver membership and also meet the Common Assessment Standard"; Platinum is "all the benefits of Gold Membership plus a one day premises audit". The Common Assessment Standard starts at Gold — Silver and below do not include it.

Who uses it: Central government departments, local authorities, NHS trusts, major Tier 1 contractors (many of whom use Constructionline as their primary supply chain register), housing associations, and utilities.

SSIP: Constructionline states that its memberships "include an SSIP from Once For All Health & Safety as standard", across Bronze, Silver, Gold and Platinum. (Constructionline is listed by SSIP as a Supporter Member rather than a registered assessment scheme.)

SafeContractor

SafeContractor is a health and safety prequalification scheme. It does not publish a full breakdown of its clients by sector; the sectors it says it covers are construction, manufacturing, facilities management, property, retail, hospitality, leisure, transport, utilities, banking and insurance, and public services.

What it assesses: Health and safety competence, risk assessment, method statements, training, and insurance. Like CHAS, it also offers extended assessment options covering environmental and quality management.

Who uses it: SafeContractor names no client list by sector, so check whether your target clients ask for it — its listed sectors include facilities management, property and retail as well as construction.

SSIP member: Yes. Core health and safety assessment is mutually recognised.

For a detailed comparison between these three schemes, see our guide: CHAS vs Constructionline vs SafeContractor: Which Do You Need?.

SSIP (Safety Schemes in Procurement)

SSIP is not itself an assessment scheme that you apply to directly. It is the umbrella body that sets the SSIP Core Criteria — the health and safety threshold standard — and manages mutual recognition between its member schemes. (The Common Assessment Standard is a separate, broader framework owned by Build UK, not by SSIP.) When someone says a contractor is "SSIP assessed," they mean the contractor holds a valid certificate from an SSIP Registered Member — such as CHAS, SafeContractor, SMAS Worksafe, Once For All Health & Safety (formerly Acclaim), CQMS, or one of the other registered assessment schemes. Constructionline is listed by SSIP as a Supporter Member rather than a Registered Member, so it does not carry out SSIP assessments itself; the SSIP inside a Constructionline membership is delivered by Once For All Health & Safety.

The key benefit for contractors: one assessment, recognised across multiple scheme members. The key limitation: mutual recognition covers the core health and safety element only. Extended modules (environmental, financial, quality) typically need separate assessment.

For a full breakdown of how SSIP works and how to choose the right member scheme, see our guide: What Is SSIP and Which Scheme Should You Choose?.

Quick-Reference Comparison Table

Feature	CHAS	Constructionline	SafeContractor
Primary focus	Health & safety	Multi-criteria prequalification register	Health & safety
Tiers	Standard, Advanced, Elite	Associate, Bronze, Silver, Gold, Platinum	Standard, Assisted, Express, Premier
H&S assessment	Yes (core)	Yes — Once For All SSIP included from Bronze; Constructionline's own H&S module from Silver	Yes (core)
Financial assessment	Elite only	Bronze+	No (core)
Environmental	Elite	Gold+	Extended option
Quality management	Elite	Gold+	Extended option
SSIP mutual recognition	Yes	Yes	Yes
Commonly associated with	Local authority, housing	Public sector, Tier 1 supply chains	No published client breakdown — its listed sectors include FM, property and retail
Pricing (published starting prices)	Standard from £429/yr; Advanced from £659; Elite from £949	Priced by turnover band and SSIP status — at the lowest band Bronze £399/yr and Gold £749 (£349 and £699 with a valid SSIP), ex VAT, rising with turnover	Standard from £419/yr; Assisted and Express from £499; Premier from £549
Published review time	Within a maximum of 10 working days (2 with Fast Track), plus any query time	Up to 10 working days for each submission to be assessed (Constructionline's membership guides), plus any query time	Within 20 working days on Standard; 5 or 2 on faster plans
Validity	12 months	12 months	12 months

Note: Prices above are each scheme's own published starting prices, all verified October 2026; review times are each scheme's own published maximum (Constructionline's is in its membership guides: "It can take up to 10 working days for a submission assessment to be completed"), and assessor queries add time. Published "from" prices are floors — CHAS and SafeContractor both state that the final fee rises with headcount, and Constructionline sets its price by turnover band in its online price calculator. Fees change regularly — always check each scheme's website for current pricing before applying. This guidance is compiled from published scheme requirements, relevant UK legislation, and the recognised industry framework (the Build UK Common Assessment Standard, which replaced the now-withdrawn PAS 91). TenderReady is not affiliated with, endorsed by, or acting on behalf of any named accreditation body or scheme.

Beyond Health and Safety: What Else Gets Assessed

While health and safety remains the cornerstone of construction prequalification, the scope of assessment has expanded significantly. Most principal contractors and public-sector buyers now expect evidence across several additional areas:

Financial Standing

Buyers want confidence that you will not go insolvent mid-project. Constructionline's Full Plan Comparison ticks "Financials" from Bronze upwards (it is "Corporate & Professional Standing" and "Health & Safety" that begin at Silver); CHAS covers financial standing at Elite. Even where a scheme does not assess this formally, expect principal contractors to run their own credit checks.

Environmental Management

An environmental policy, waste management procedures, and (for larger contracts) an Environmental Management System aligned to ISO 14001. This is increasingly a baseline expectation, not a differentiator.

Equal Opportunities and Diversity

A written equal opportunities policy and evidence of fair recruitment practices. Constructionline assesses this in its Equal Opportunity and Diversity module at Gold, and CHAS through the Common Assessment Standard at Elite.

Modern Slavery

A modern slavery statement (mandatory for businesses with a turnover of £36 million or more, but increasingly expected as good practice for smaller firms), evidence of supply chain due diligence, and worker welfare procedures.

Quality Management

Documented quality procedures, inspection and test plans, defect management, and (for larger firms) a Quality Management System aligned to ISO 9001.

For a detailed breakdown of what assessors check across all these areas, see our guide: Construction Accreditation Requirements: What Tier 1 Contractors Actually Check.

Which Scheme Should You Get First?

This is the question every SME contractor asks, and the answer depends on your target market:

If you work primarily for local authorities or housing associations: CHAS is typically the most recognised and often the most requested.

If you are targeting Tier 1 contractor supply chains or public-sector frameworks: Constructionline (at least Silver, often Gold) is frequently a mandatory requirement. Many Tier 1 contractors use Constructionline as their primary supply chain database.

If you work in facilities management, maintenance, or commercial fit-out: check whether your clients name SafeContractor — facilities management, property and retail are among the sectors it says it covers.

If budget is tight: Start with one scheme. Thanks to SSIP mutual recognition, you gain visibility across the wider network. CHAS Standard is often the most accessible entry point for SMEs.

If you want maximum coverage: Many established SMEs hold two or even all three, particularly if they work across multiple sectors. The investment is significant but opens the widest range of opportunities.

How to Prepare for Prequalification Assessment

Regardless of which scheme you pursue, the documentation requirements overlap substantially. Getting your house in order before you apply saves time, reduces the risk of failure, and ensures your systems are genuinely robust — not just paperwork exercises.

Core Documentation You Need

Health and safety policy — Signed by a director, reviewed within the last 12 months, specific to your operations (not a generic template).
Risk assessments — Activity-specific, regularly reviewed, demonstrating genuine engagement with the hazards your workforce faces.
Method statements and RAMS — Showing how you plan and control high-risk activities on site.
Insurance certificates — Employers' liability (minimum £5 million by law under reg 3(1) of the Employers' Liability (Compulsory Insurance) Regulations 1998, though most principal contractors require £10 million), public liability, and professional indemnity where applicable.
Training records — CSCS cards, SMSTS/SSSTS, trade-specific qualifications, and evidence of ongoing CPD.
Environmental policy — Appropriate to your scale, covering waste management, pollution prevention, and environmental awareness.
Equal opportunities policy — Written policy with evidence of implementation.
Modern slavery statement — Even below the statutory threshold, a proportionate statement demonstrates supply chain awareness.

Use our Health & Safety Documentation Checklist to audit your current position before applying.

Common Reasons for Failure

Assessment bodies report that a significant proportion of first-time applicants are referred back for additional information or fail outright. The most common issues include:

Generic, template policies that have not been tailored to the business or its activities
Out-of-date documents — particularly health and safety policies not reviewed in the last 12 months
Missing or incomplete risk assessments for core activities
No evidence of competent health and safety advice (either in-house or through an external consultant)
Insurance gaps — policies that have lapsed, or cover levels below client requirements
Lack of training records — particularly for site supervisors (SMSTS/SSSTS) and operatives (CSCS)

Using TenderReady to Assess Your Readiness

Before you spend money on application fees, it pays to understand where you stand. Our Construction Accreditation Readiness Scorer analyses your current documentation, policies, and management systems against the criteria used by the major schemes, giving you a clear picture of what needs work before you apply.

Summary

UK construction prequalification is built around a handful of key schemes — CHAS, Constructionline, and SafeContractor — operating under the SSIP umbrella and aligned to the Common Assessment Standard. Understanding which scheme (or schemes) your target clients recognise, preparing your documentation thoroughly before applying, and maintaining your systems year-round rather than scrambling at renewal time will put your business in the strongest possible position.

Start by assessing your readiness with our Construction Accreditation Readiness Scorer, then work through the specific documentation requirements using our Health & Safety Documentation Checklist.

Sources and References

Health and Safety at Work etc. Act 1974 — legislation.gov.uk
Management of Health and Safety at Work Regulations 1999 — legislation.gov.uk
Construction (Design and Management) Regulations 2015 — legislation.gov.uk
Common Assessment Standard (replaced PAS 91 in 2023) — Build UK
PAS 91:2013+A1:2017, Construction prequalification questionnaires — catalogue record showing status "Withdrawn", withdrawal date "21 Apr 2023" — BSI Knowledge
PPN 03/24, paragraph 7 — "removed references to PAS91 which has now been withdrawn by the BSI" — Cabinet Office (PDF)
CHAS contractor products and packages (published membership prices) — chas.co.uk
CHAS FAQ ("reviewed within a maximum of 10 working days"; Fast Track "a maximum of 2 working days") — chas.co.uk
SafeContractor contractor pricing plans (published starting prices; Standard "Assessment review within 20 working days") — safecontractor.com
SafeContractor homepage ("Sectors we cover") — safecontractor.com
Constructionline subcontractor memberships — Full Plan Comparison (Financials ticked from Bronze; prices by turnover band in its price calculator) — constructionline.co.uk
Constructionline — "Constructionline is part of the Once For All Group" — constructionline.co.uk/about
SSIP member register (Registered Member vs Supporter Member) — ssip.org.uk
SSIP Core Criteria for the demonstration of organisational capability — the scope of an SSIP assessment, and the "exemption against Section 4 of the CAS" — ssip.org.uk
Common Assessment Standard — "an industry-agreed question set and corresponding assessment standards", desktop and site-based certification levels — builduk.org
Employers' Liability (Compulsory Insurance) Act 1969 (the duty to insure) — legislation.gov.uk
Employers' Liability (Compulsory Insurance) Regulations 1998, reg 3(1) (the £5 million amount) — legislation.gov.uk
Modern Slavery Act 2015 — legislation.gov.uk
SSIP (Safety Schemes in Procurement) — ssip.org.uk
Constructionline Silver Membership Guide v7 — "It can take up to 10 working days for a submission assessment to be completed" (p.5) — constructionline.co.uk (PDF)

Disclaimer: The guidance in this article is based on publicly available information and common industry practice. TenderReady is not affiliated with, endorsed by, or acting on behalf of CHAS, Constructionline, SafeContractor, SSIP, BSI, or any other named accreditation body or scheme. Requirements and pricing are subject to change — always verify current details with the relevant scheme directly.