Qualifying a site-services supplier properly takes more than checking a logo strip on their website. Buyers who get this wrong inherit the risk, whether that is a Health and Safety Executive enforcement notice, a contractor who cannot mobilise on the date promised, or a subcontractor who cannot survive a 90-day payment cycle. This article sets out the evaluation criteria a principal contractor's procurement team, or an estates and facilities director doing due diligence on a security, cleaning, construction support, vacant property or fire protection supplier, should actually be checking, and why each one matters.

Qualifying a site-services supplier properly takes more than checking a logo strip on their website. Buyers who get this wrong inherit the risk, whether that is a Health and Safety Executive enforcement notice, a contractor who cannot mobilise on the date promised, or a subcontractor who cannot survive a 90-day payment cycle. This article sets out the evaluation criteria a principal contractor's procurement team, or an estates and facilities director doing due diligence on a security, cleaning, construction support, vacant property or fire protection supplier, should actually be checking, and why each one matters.

1. Accreditations and SSIP membership

What SSIP is, and why it exists

Safety Schemes in Procurement (SSIP) is not itself an accreditation. It is a mutual recognition framework covering a group of independent health and safety pre-qualification assessment schemes. A supplier who holds current certification from one SSIP-recognised scheme does not need to be separately reassessed by another scheme a buyer happens to use, because the schemes recognise each other's assessments through SSIP's "Deem to Satisfy" agreement. This exists specifically to cut duplicated paperwork and cost for both buyers and suppliers, and it has done so at meaningful scale: SSIP reported over 90,000 suppliers registered across its member schemes as of January 2026.

CHAS, SafeContractor and Constructionline are the three schemes most commonly encountered in UK construction and FM procurement, with Achilles and Builders Profile also SSIP-recognised and in regular use. A buyer asking "are you SSIP accredited" is really asking whether a supplier holds a current, verifiable assessment from any one of these, checkable directly on the SSIP Portal rather than taken on trust from a supplier's own marketing.

What to actually check

• The certificate is current, not expired or "in renewal" without a stated date.
• The scope of assessment matches the work being procured (a scheme assessment for office cleaning does not automatically cover high-risk construction support work).
• The certificate number is verifiable independently, not just quoted.

AOG's own accreditation register is a reasonable worked example of what a complete answer looks like: current membership spans CHAS (Elite tier), SafeContractor, PQS, Constructionline (Gold and Social Value tiers) and Builder's Profile, alongside sector-specific memberships such as BICSc for cleaning and FORS Champion for fleet operations. It is also worth noting that a properly maintained register will honestly show a scheme mid-renewal rather than silently dropping it or overstating its status. That is what a buyer should expect to see, not a page that only ever shows green ticks.

2. ISO certification: what each one actually signals

ISO certificates get treated as interchangeable proof of "quality" far too often. Each one certifies a different management system, and a competent evaluator should know what each is actually testing.

ISO 9001 (quality management)

Certifies that a supplier has a documented, auditable quality management system covering how work is planned, delivered and corrected when it goes wrong. It says nothing about safety or environmental performance on its own.

ISO 14001 (environmental management)

Certifies a systematic approach to managing environmental impact, waste, and resource use. Relevant to any supplier handling waste streams (vacant property clearance, construction support) or operating vehicle fleets.

ISO 45001 (occupational health and safety management)

Certifies a management system for identifying and controlling workplace health and safety risk. This is the one buyers most often confuse with SSIP accreditation. They are not the same thing: SSIP schemes assess a supplier's health and safety competence against a common question set, while ISO 45001 certifies an ongoing management system audited annually by a UKAS-accredited certification body. A supplier holding both is demonstrating two different, complementary things.

3. Financial standing and due diligence

Buyers check financial standing because a supplier that cannot fund payroll, materials or subcontractor payments through a contract's duration is a live delivery risk, independent of how good their method statement looks. A proper financial standing check typically covers: filed accounts and their age (via Companies House), credit rating from a recognised agency, turnover relative to the contract value being bid, and evidence of adequate working capital or parent company guarantee where relevant.

Worth knowing for anyone running pre-qualification: PAS 91, the long-standing construction pre-qualification questionnaire standard, was formally withdrawn by the British Standards Institution in April 2023. Government guidance issued via Procurement Policy Note 03/24 now directs public sector buyers toward the Common Assessment Standard (CAS), developed by Build UK with Constructionline, as the preferred pre-qualification framework, particularly for projects above the relevant public procurement threshold. A supplier's financial standing question set has therefore moved on structurally in the last two to three years; a buyer still referencing PAS 91 by name in their own PQQ is working from a withdrawn standard.

4. Social value

Social value is not a soft add-on in public sector tenders; it is a statutory consideration. The Public Services (Social Value) Act 2012 requires public bodies procuring services in England and Wales to consider how the services being procured might improve the economic, social and environmental wellbeing of the area, and to consider this before the procurement process starts, not retrofitted afterwards.

Central government procurement has moved further since. Procurement Policy Note 002 set out the original central government Social Value Model; that guidance was itself superseded by PPN 026 in August 2026, which is the current live guidance for how social value should be weighted and evidenced in central government procurement. Under the Procurement Act 2023, contracting authorities are legally required to "have regard" to the National Procurement Policy Statement, which has also been updated to align with this social value guidance.

Practically, this means a supplier bid that treats social value as a paragraph of generic community-benefit language, rather than measurable, contract-specific commitments (local employment, apprenticeships, targeted social value spend), will score worse against a properly weighted evaluation matrix. AOG's Constructionline Social Value accreditation is one example of the kind of evidenced, third-party-assessed commitment a buyer should be looking to see, rather than a supplier's own unverified claim.

5. References and track record

A reference check should go beyond "would you use them again." Ask for:

• A named contact who was involved in day-to-day delivery, not only a relationship-level sponsor.
• At least one reference from a contract of comparable scale and risk profile to the one being tendered, not just the supplier's largest or newest logo.
• How the supplier handled something going wrong, not only how smoothly things ran when nothing did.

A supplier who cannot produce a reference from a comparable, recent, verifiable contract is telling a buyer something, even if they never say it directly.

6. Mobilisation capability

Mobilisation speed is one of the easiest claims to make and one of the hardest to verify without pressing for specifics. Rather than accepting a stated number of days, ask:

• What exactly happens in the first 24 to 72 hours after contract award: recruitment, vetting, equipment, uniforms, site induction?
• Who is the named mobilisation lead, and are they dedicated to this account or shared across several live mobilisations?
• What has actually caused a mobilisation to slip on a previous contract, and what changed as a result?

A supplier who can answer these with specifics is demonstrating a repeatable process. A supplier who answers only with a headline number is demonstrating a marketing line.

7. Insurance levels appropriate to scope

Employers' liability insurance is a statutory minimum in the UK under the Employers' Liability (Compulsory Insurance) Act 1969: at least £5 million cover from an FCA-authorised insurer, enforced by the HSE, for any business employing staff. That is a floor, not a ceiling. Public liability and, where relevant, professional indemnity cover should be assessed against the actual scope and risk profile of the contract being tendered, not accepted as a single generic certificate covering every service line a supplier offers. A supplier operating across security, construction support and fire protection divisions, for example, carries a materially different risk profile per division, and a buyer evaluating one specific scope of work should ask to see the certificate that actually applies to it.

8. CDM 2015 duties, where relevant

Where a site-services contract touches construction work, buyers and suppliers both sit inside the Construction (Design and Management) Regulations 2015 (CDM 2015), enforced by the HSE. CDM 2015 sets duties across five dutyholder roles: client, principal designer, principal contractor, contractor and worker. On any project involving more than one contractor, a principal designer must be appointed to plan and coordinate health and safety through the pre-construction phase, and a principal contractor appointed to do the same through the construction phase.

A project becomes notifiable to the HSE (via an F10 notification, under Regulation 6) if construction work will either last longer than 30 working days and involve more than 20 workers on site at any one time, or exceed 500 person-days of work in total, whichever threshold is met first. A supplier bidding into construction-adjacent site services, such as construction support labour or fire remediation work, should be able to state clearly which CDM dutyholder role they expect to sit in on a given contract, and should never be vague about whether a project crosses the notification threshold. If they cannot answer that question precisely, that is a due diligence flag in itself.

The short version

A supplier worth qualifying should be able to produce, without hesitation: a current, scope-matched SSIP certificate; the specific ISO certifications relevant to the work (not a blanket claim of "ISO certified"); evidence of financial standing appropriate to the contract value; a measurable, evidenced social value commitment where the tender is public sector; contactable references from comparable recent contracts; a specific mobilisation plan rather than a headline number; insurance certificates matched to the actual scope; and, where construction work is involved, clarity on their CDM 2015 dutyholder role. Anything less than that is a marketing claim, not a due diligence answer.

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