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CDM 2015 and Subcontractor Documentation

Updated May 2026 — Covers the Construction (Design and Management) Regulations 2015

The Construction (Design and Management) Regulations 2015 (CDM 2015) place specific duties on principal contractors to manage health and safety across a construction project. One of the most practical day-to-day implications of these duties is the need to collect, verify, and maintain documentation from every subcontractor working on the site.

This guide explains what CDM 2015 requires, how it affects subcontractor documentation, and what a principal contractor needs to have in place before and during work on site.

Which projects does CDM 2015 apply to?

CDM 2015 applies to virtually all construction work in Great Britain. The extent of the duties that apply depends on the project type:

• Notifiable projects — those lasting more than 30 working days with more than 20 workers simultaneously, or exceeding 500 person-days total. These require notification to the HSE and the appointment of a Principal Designer and Principal Contractor.
• All other construction projects — CDM 2015 still applies; the duties are simply distributed differently depending on whether there is more than one contractor.

Principal Contractor duties relevant to subcontractors

Under CDM 2015, the Principal Contractor has a duty to plan, manage, monitor and coordinate the construction phase. In relation to subcontractors, this means:

• Ensuring subcontractors are competent — the PC must take reasonable steps to satisfy themselves that subcontractors have the skills, knowledge, experience and organisational capability to carry out the work safely.
• Providing the construction phase plan — relevant parts of the plan must be shared with subcontractors before they begin work.
• Coordinating health and safety — the PC is responsible for the overall management of site health and safety, including ensuring subcontractors comply with their own obligations.
• Collecting and maintaining documentation — while CDM 2015 does not specify exactly which documents to collect, the competence duty requires a structured approach to pre-qualification and ongoing compliance.

What "competence" means under CDM 2015

CDM 2015 replaced the previous requirement to assess competence with a broader duty to take "reasonable steps" to satisfy yourself that workers and contractors are capable of doing their work without putting people at risk. In practice, courts and the HSE look at whether a principal contractor had a documented, consistent approach to competence assessment.

For subcontractors, this typically means collecting and retaining evidence of:

• Relevant qualifications and trade memberships (CSCS cards, Gas Safe, NICEIC/NAPIT)
• Health and safety management capability (H&S policy, risk assessment procedures)
• Experience of similar work (references, previous contracts if significant)
• Adequate insurance (Public Liability and Employers Liability as a minimum)

Documents to collect before a subcontractor starts work

While the specific documents will depend on the type of work, a robust CDM-compliant approach for most subcontractors would include:

• Current Public Liability Insurance certificate (with expiry date confirmed)
• Current Employers Liability Insurance certificate (legally required if they have employees)
• Health and Safety Policy (required by law for 5+ employees; good practice for all)
• Task-specific Risk Assessment covering the work on your site
• Task-specific Method Statement (RAMS) for high-risk activities
• Evidence of workers' competence (CSCS cards, trade certificates)
• Any scheme accreditation relevant to the work (Gas Safe, NICEIC, NAPIT, etc.)

The Construction Phase Plan and subcontractors

The Construction Phase Plan (CPP) is a document the Principal Contractor must prepare before the construction phase begins. It should be shared with subcontractors to the extent relevant to their work. Subcontractors' RAMS should be consistent with the CPP — if a subcontractor's method statement conflicts with site-wide controls in the CPP, that needs to be resolved before work begins.

When things go wrong — the documentation question

If a subcontractor is involved in an accident or incident, one of the first questions the HSE will ask is: what steps did the Principal Contractor take to satisfy themselves that the subcontractor was competent and working safely?

A documented compliance record — showing which documents were collected, when, and what was checked — is the most important evidence a PC can have. Verbal assurances or informal arrangements provide little protection.