Why the first morning on site is too late
A new subcontractor turns up, the job starts, and the paperwork is a photo of an insurance certificate on WhatsApp and a promise to send the UTR later. Then the first invoice arrives and you can’t pay it properly: HMRC hasn’t verified them, you don’t know whether to apply the reverse charge, and the certificate photo has expired.
Everything below can be collected before they start, from their phone, in ten minutes. The list is the same for every subcontractor, so build it once.
What HMRC needs: CIS verification
Under the Construction Industry Scheme you must verify a subcontractor with HMRC before you first pay them. HMRC tells you whether to pay them gross, with the standard deduction, or with the higher deduction because they aren’t registered. The details you give have to match what they registered with. See gov.uk on verifying subcontractors.
- Sole trader: full name, Unique Taxpayer Reference (UTR) and National Insurance number.
- Limited company: company name, company UTR and company registration number.
- Partnership: partnership name, partnership UTR and the nominated partner’s details.
Ask for these in a form, not in a message, so the numbers arrive typed and complete. HMRC has rules on when a subcontractor you have used before needs verifying again; check the current guidance rather than assuming.
VAT: the domestic reverse charge
For most building and construction services between VAT-registered businesses that are reported under CIS, the customer accounts for the VAT instead of the supplier. Whether it applies to a subcontractor’s invoice to you depends on their VAT status, yours, and whether you are an end user for that work. See HMRC’s guidance on the reverse charge.
- Their VAT number, or confirmation that they aren’t VAT registered. If they aren’t, the reverse charge can’t apply to their invoices.
- Your own position in writing. If you are the end user or an intermediary supplier for a job, tell the subcontractor in writing at or before the time of supply, and keep a copy; HMRC asks for these on inspection.
Right to work: the checks now reach subcontractors
Right to work checks used to be an employer’s duty for employees. From 1 October 2026 the regime was extended under the Border Security, Asylum and Immigration Act 2025 to businesses that engage individual subcontractors and other workers who are not employees, with construction named as a focus. The civil penalty for a breach runs to tens of thousands of pounds per worker. Construction Enquirer on the October 2026 start; gov.uk on how to check.
- For a sole trader: the documents the Home Office guidance lists for a manual check, or the share code and date of birth for an online check. Digital checks of a British or Irish passport must go through a registered provider.
- For a company that sends its own staff: written confirmation in your subcontract that they carry out right to work checks on everyone they send, and the right to see evidence.
Insurance, competence and site paperwork
Commonly asked for, with the dates that matter:
- Public liability insurance certificate, showing the insurer, the cover limit and the expiry date. Note the expiry; most certificates run a year.
- Employers’ liability insurance if they employ anyone, which is a legal requirement for most employers. See gov.uk.
- Trade registration where the work needs it: a Gas Safe registration number for gas work, the registration body for electrical work, and so on. Check numbers on the register, not just the card.
- Cards and qualifications the site or client asks for, such as a CSCS card and any plant tickets, with expiry dates.
- Risk assessments and method statements for the work they will do, if your site or client requires them before anyone starts.
- Bank details and payment terms, ideally confirmed in writing by the subcontractor rather than taken from an invoice.
- Your subcontract or terms, signed. A drawn or typed electronic signature is fine for ordinary subcontract terms.
- An emergency contact.
A subcontractor pack you can copy
- 1A details form: trading name and legal name, business type, UTR, National Insurance number or company number, VAT number or “not registered”, address, bank details, emergency contact.
- 2Uploads: public liability certificate, employers’ liability certificate if they have staff, trade registration, cards and tickets, risk assessments and method statements if required.
- 3Right to work evidence, in the form the current Home Office guidance asks for.
- 4Your subcontract terms, to sign.
- 5A tick to confirm the details are correct and they will tell you when a certificate is renewed.
Run the CIS verification and the reverse charge decision once the pack is in, and put the certificate expiry dates in your diary so you can ask for the renewals before they lapse.
How PORTALD does it
- 1Add the subcontractor as a customer and send them the pack as one checklist: a form for the details, an upload for each certificate, and your terms as a contract they sign online.
- 2They open one link on their phone, take photos of the certificates and sign, without an app.
- 3Switch on an AI check for the certificates, in your words, such as “a public liability insurance certificate that is in date today, showing the insurer and the cover limit”. A blurred photo or an expired certificate is flagged for both of you straight away.
- 4See every subcontractor’s pack in one place, with what is in and what is still missing, and send a reminder when you choose. When a certificate is due to lapse, ask for the new one through the same checklist.
See the customer portal for builders and the AI document checker for how the checks look.
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Common questions
What do I need from a subcontractor to verify them with HMRC?
For a sole trader, their full name, UTR and National Insurance number. For a limited company, the company name, company UTR and registration number. For a partnership, the partnership name and UTR and the nominated partner's details. The details must match what they registered with HMRC.
Does the VAT reverse charge apply to every subcontractor invoice?
No. It applies to most construction services reported under CIS between VAT-registered businesses, unless the customer has told the supplier in writing that it is an end user or intermediary supplier. If the subcontractor isn't VAT registered it can't apply. Collect their VAT number or confirmation that they have none, and keep your written notices.
Do I have to check a self-employed subcontractor's right to work?
From 1 October 2026 the right to work regime was extended to businesses that engage individual subcontractors and other non-employees, with construction a named focus. Read the current Home Office employer guidance for who is in scope and what counts as a compliant check, and make sure your contracts with labour suppliers cover it.
How often should I ask for a subcontractor's insurance certificate?
Every time it is renewed, which for most policies is yearly. Record the expiry date when the certificate arrives and ask for the new one before it lapses, rather than finding out on site.
Does PORTALD verify subcontractors or check right to work?
No. PORTALD collects the details, certificates and signed terms in one checklist and shows what is still missing. CIS verification, the reverse charge decision and right to work checks stay with you, using HMRC's services and the Home Office guidance.