How to onboard a subcontractor: CIS, insurance and cards

Onboarding a subcontractor means having five things on file before their first day on site and their first payment: the details to verify them with HMRC under the Construction Industry Scheme (CIS), their insurance, their cards, the paperwork for the job and, for an individual you engage directly, a right to work check. Ask for everything once, on the day the order is placed, and give one person the gaps. An AI worker can do the asking, the reading and the chasing. The verifying, the checking and the approval stay with your people.

Who handles a new subcontractor today?

The trigger is a contracts manager agreeing a subcontractor for a job, often for Monday. From there the file is usually the office manager's or the bookkeeper's. The office finds out what is missing when the first invoice arrives, or at the site gate.

How do you build a subcontractor's file, step by step?

1. Send one pack on the day of the order. Put every request in one email, with one list.

2. Collect the CIS details in the form HMRC holds them. Nobody new is paid until HMRC has verified them. For a sole trader that takes the UTR and National Insurance number; for a limited company the company name, company UTR and registration number; for a partnership the nominated partner's details, the trading name and the partnership UTR. GOV.UK says they must match the subcontractor's registration exactly, so ask for the registered name, not the name on the van.

3. Verify, and record the rate. HMRC's answer is whether they are registered and which rate applies: 20%, 30% for one who is not registered, or no deduction with gross payment status. Put it on the file with the date. Someone you have used before goes through verification again if you have not included them on a CIS return in the current or last two tax years.

4. Consider employment status. GOV.UK says a contractor must check whether the person should be employed instead of subcontracted, and that a penalty may follow if they should have been an employee.

5. Read the insurance certificate, not just its filename. Check the insured name against the order, the cover and limit against your subcontract, and the expiry date. A quotation is not a certificate. Diarise the expiry on the day you file it.

6. Check the cards. A CSCS card is not a legal requirement, but most principal contractors and major house builders require one on their sites. CSCS Smart Check verifies a card and shows its type, the qualifications behind it and its expiry date. Record it for every operative who will attend.

7. Right to work, for individuals you engage. Under the Home Office's employer's guide of 1 October 2026, which applies across the UK, an employer includes a person who engages an individual sub-contractor. An employer found to be employing someone illegally, without the prescribed checks, may face a civil penalty of up to £60,000 per illegal worker; for an individual sub-contractor, only where the engagement began on or after 1 October 2026. One of the prescribed checks is done before the work starts. Where workers reach your site through a chain of contracts, the guide's own example is a construction company that may be treated as their employer and may be liable for a penalty; its statutory excuse rests on prescribed requirements for the contractual arrangements, where those were entered into on or after the same date. This article does not advise on them.

8. Job paperwork and approval. Collect the risk assessments and method statements for this job, any accreditation you ask for such as CHAS or Constructionline, and bank details confirmed by a phone call to a number you found yourself, not the one on the email. Then one person approves the subcontractor to start.

Which steps can an AI worker take on?

In this job an AI worker can send the pack on the day the contracts manager asks, read each document as it arrives and compare it with your requirements: does the insured name match, has the policy expired, is every operative's card listed. It can chase what is missing by email, tell the contracts manager on Thursday who is not ready for Monday, put the finished file together with its exceptions, and diarise every expiry date. The role is described on our page for supplier onboarding, and the dates it then watches on renewals and expiry tracking.

What waits for a person, and why

• CIS verification and the deduction. This is the contractor's duty to HMRC, done by your accounts person.

• Employment status. It turns on facts that are in no document.

• The right to work check. The Home Office guide says the employer is responsible for carrying out the check; an outside party may only support it, with gathering information and the technical side. An AI worker can ask for the share code, as set out under right-to-work checks. A person does the check.

• Bank details. A person confirms them, by phone. An AI worker never moves money.

• Any exception. A limit below your requirement, a card of the wrong type, a start before the file is complete: the contracts manager decides.

What to have ready before you start

You need a written list of what you require from each kind of subcontractor (labour only, a specialist firm, a sole trader), the insurance limits your own contracts pass down, and one place where the file lives, with one named approver. With those you can send a single pack tomorrow. Our article on scaling a construction company without hiring covers the office's other loads. The rest of a contractor's office work, from CIS returns to applications for payment, is on our page for construction contractors.

For a contractor an AI worker would ask for each subcontractor's file, read it and chase the gaps before the first day on site, while your accounts person verifies and your contracts manager approves. Talk to our agent before another subcontractor starts on site with an unfinished file.