The subcontractor paperwork that protects you when something goes wrong
If a subcontractor has an accident on your site and your documentation isn't in order, you're liable. Here's exactly what you need, when, and why.
The problem
You bring in an M&E firm to handle the electrical fit-out. They've been on site three weeks. One of their workers falls from a ladder. The HSE inspector arrives.
The first thing the inspector asks for isn't a description of the accident. They ask for the Construction Phase Plan, the subcontractor's risk assessments, and proof that the worker had the right training for the task. If you can't produce that documentation on the spot — you're in the frame, even if the accident had nothing to do with your crew.
Why the principal contractor is liable even when it isn't their fault
CDM 2015 puts the responsibility on you
The Construction (Design and Management) Regulations 2015 are the main legal framework governing how construction work is planned, managed and carried out in the UK. Under CDM 2015, the Principal Contractor — the company or individual in charge of the construction phase — has a legal duty to plan, manage and monitor the work of every contractor on site.
That duty doesn't disappear when you subcontract a package. Section 15 of CDM 2015 requires the Principal Contractor to ensure that every contractor they appoint has the skills, knowledge, training and experience to carry out their work safely. If they don't, and someone gets hurt, you've failed in your statutory duty.
This isn't a technicality. The Health and Safety at Work etc. Act 1974 (Section 3) extends your duty of care to non-employees — including subcontractors' workers — on your site. The HSE's enforcement position is clear: "I didn't know" is not a defence when you're the Principal Contractor.
Personal liability under HSWA 1974
Section 37 of the Health and Safety at Work Act creates personal criminal liability for directors, managers and site managers when an offence is committed with their consent, connivance or neglect. If the HSE finds that a site manager knew the subcontractor's workers lacked proper training and did nothing about it, they can be prosecuted individually — not just the company.
Following the Sentencing Council's 2016 Health and Safety Offences guidelines, fines for large organisations can reach millions of pounds. For individuals, custodial sentences are possible in the most serious cases. The era of token fines for construction H&S failures is over.
Civil liability doesn't stop at the site gate
When an injured subcontractor's worker makes a civil claim, the courts will look at the entire chain of responsibility. If the Principal Contractor failed to verify the subcontractor's competence, failed to ensure an adequate Construction Phase Plan was in place, or allowed work to proceed without proper risk assessments — they will typically be found jointly and severally liable alongside the subcontractor.
That liability is separate from the subcontractor's employers' liability insurance. If the subcontractor's insurer disputes the claim, or the subcontractor turns out to be uninsured, you're the one left holding the bill.
What documentation you need — and when
Before the subcontractor sets foot on site
This is the documentation that must be in place before the first worker from any subcontracting firm arrives:
Company credentials:
- Companies House registration or proof of legal trading status.
- Public Liability Insurance certificate with a current schedule — minimum £1m, typically £2-5m for most construction packages. Check the expiry date, not just the certificate.
- Employers' Liability Insurance certificate — legally required under the Employers' Liability (Compulsory Insurance) Act 1969, minimum £5m. No EL insurance means they cannot legally employ workers on your site.
Tax and HMRC status:
- Verification of CIS (Construction Industry Scheme) registration. If a subcontractor isn't registered with CIS, you're legally required to deduct 30% tax from their payments rather than the standard 20%. Unregistered subcontractors are a red flag — it often indicates a company that isn't running its affairs properly.
- UTR (Unique Taxpayer Reference) for self-employed individuals.
Competence and training:
- CSCS cards (Construction Skills Certification Scheme) for all workers on site. Not a legal requirement per se, but required by virtually every principal contractor's site rules and a standard industry benchmark for demonstrating H&S competence. Check the card type matches the worker's role.
- Training records for any task-specific certifications: IPAF for MEWP, PASMA for mobile towers, asbestos awareness, confined spaces, etc.
Health and safety documentation:
- The subcontractor's Method Statement and Risk Assessment (RAMS) for every work package before it starts — not a generic document, specific to the tasks on your site.
- Evidence of their Health and Safety policy (required by law for firms with 5 or more employees under HSWA 1974 Section 2).
- Their competent person for H&S matters (required under the Management of Health and Safety at Work Regulations 1999).
Your Construction Phase Plan must cover subcontractors
Under CDM 2015, the Principal Contractor must produce and maintain a Construction Phase Plan before any construction work begins. This isn't a static document — it must be updated as subcontractors join the project.
The Plan must address:
- How subcontractor activities will be coordinated to avoid conflicts and shared risks.
- Site induction arrangements: every worker from every subcontractor must receive a site-specific induction before starting work, and you must keep a record of attendance.
- Emergency procedures communicated to all subcontractors.
- How you'll monitor compliance with the Plan throughout the project.
The Construction Phase Plan is one of the first things an HSE inspector will ask for. A generic, undated document that clearly hasn't been updated for the project is treated as no plan at all.
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During the works
Documentation is not a one-off exercise at the start. It's an ongoing obligation:
- Insurance renewals: diarise subcontractor insurance expiry dates. A policy that lapses mid-project leaves a gap in cover that's your problem as much as theirs.
- New workers: every new operative from a subcontractor needs a site induction, CSCS card check and confirmation of relevant training before they start — not on their second day.
- Changes in scope: if the subcontractor takes on tasks beyond their original package, their RAMS must be updated before those tasks begin.
- CIS payments: verify CIS status each time you add a new subcontractor or self-employed individual. HMRC's CIS online service lets you verify in real time.
How long to keep the records
| Document | Minimum retention | Basis | |----------|------------------|-------| | Construction Phase Plan | 3 years post-completion | CDM 2015 / HSE guidance | | RAMS and induction records | 3 years | HSE guidance | | Employers' and Public Liability insurance schedules | 40 years (EL) / 6 years (PL) | EL Regulations 1998 / Limitation Act 1980 | | CIS records and payments | 3 years | HMRC CIS regulations | | Accident records (RIDDOR) | 3 years from date of entry | RIDDOR 2013 | | Civil claims documentation | 15 years | Limitation Act 1980 (latent damage) |
The 40-year retention for Employers' Liability insurance schedules catches most people out. Occupational disease claims — asbestos, vibration white finger, noise-induced hearing loss — can surface decades after the work was done. You need to be able to prove who was insured and for how much.
What happens when the paperwork isn't there
The HSE has three main enforcement tools, and they use them:
Fee for Intervention (FFI): when an inspector finds a material breach of H&S law, they charge the dutyholder £163 per hour for the time spent identifying the breach, investigating and taking enforcement action. A routine site visit that uncovers missing RAMS and inadequate induction records can quickly run to thousands of pounds — before any formal action.
Improvement and Prohibition Notices: an Improvement Notice gives you a deadline to comply. A Prohibition Notice stops the work immediately. Both are public record and can affect your ability to bid for public sector contracts.
Prosecution: following the 2016 Sentencing Guidelines, courts consider turnover when setting fines. A medium-sized contractor (£10m-£50m turnover) can face fines of £250,000 to £700,000 for a serious H&S offence. An individual site manager convicted under Section 37 HSWA faces an unlimited fine and up to two years' imprisonment for the most serious cases.
Conclusion
Subcontractor documentation isn't bureaucracy. It's the only thing standing between you and joint liability when something goes wrong on your site.
The failure mode is almost always the same: the documents exist somewhere, but nobody can find them. They're in email threads, in a filing cabinet in the office, on a laptop that's been replaced. When the HSE inspector arrives and asks for the subcontractor's RAMS for the work that was happening when the accident occurred — you need to produce it in minutes, not days.
Get it before they start. Update it when things change. Keep it where you can find it in an emergency. That's the whole system.
If you also need site visit documentation that holds up as legal evidence, read why WhatsApp photos don't work in court — and what does.