Contractor Document Verification for Staffing Agencies: Status, Insurance and Registration

This article is for information only and is not legal advice. Regulatory references are accurate at the date of publication. Consult a qualified professional before deciding on any individual file.

Contractor document verification means checking, before the first day of work, that a self-employed person is properly registered, correctly classified for tax, insured for the work they will actually do, and that every document in the file tells the same story. It compares names, registration numbers, dates and policy terms against official registers and against each other. It does not prove a document is genuine. This guide covers the documents to request, what each must show, and the mismatches that should stop a start date, using UK rules as the reference.

Why a contractor file is not a temp worker file

A temp worker is on the agency's payroll or an umbrella's; a genuine contractor is a business that carries its own tax, insurance and risk. Agency workers fall under the Agency Workers Regulations 2010 and the Conduct of Employment Agencies and Employment Businesses Regulations 2003. A contractor does not, but the agency or end client takes on a different risk: wrongly treating an employee as self-employed.

That risk has a name in the UK: IR35. Under the off-payroll working rules in Chapter 10 of ITEPA 2003, medium and large clients (and agencies in the chain) must decide the worker's employment status for tax and issue a Status Determination Statement. A file with no basis for that decision is a liability.

For the employee side of the business, see our guides on temp worker verification before a first assignment and staffing agency compliance requirements.

Which documents to request from a self-employed contractor

A usable contractor file holds six items: proof of identity, proof of registration, a tax reference, insurance certificates, a contract or statement of work, and a bank account in the business's name.

Employers' liability insurance is compulsory for UK businesses with employees, with a minimum cover of £5 million (HSE guidance). A sole trader without staff is exempt, so the absence of the certificate is not automatically a gap. The file should record why.

For limited companies, confirm status on Companies House: a company with a "strike-off action" notice or overdue accounts is a signal, even if the contractor looks real.

Employed or self-employed: what the file can and cannot tell you

No document decides status; the working arrangement does, and HMRC's own checks look at control, substitution and mutuality of obligation. HMRC's Check Employment Status for Tax tool is the starting point for the decision, and the agency should keep the output.

The file can show warning signs:

• the contractor has invoiced only one client for the last 12 months;
• the incorporation date is days before the first engagement;
• the contract names a personal substitute right that no one intends to use;
• the stated activity (SIC code, insurance wording) differs from the actual role;
• payment is a fixed day rate for hours set by the client, with no deliverable.

None of these proves misclassification. Several together warrant a second look from someone qualified before the start date.

Insurance: check the scope, not only the expiry date

A certificate that is valid today can still exclude the job. Three checks catch most problems:

1. The policy period covers the whole engagement, not just the signature date.
2. The insured activities include the work in the statement of work.
3. The named insured is the contracting entity, the same legal name and number as on the registration extract.

Where the contractor will work on client premises, the client's own site rules may also set minimum limits, so the agency should compare the certificate against the client contract before sending anyone.

Where contractor files contradict themselves

Most mismatches are clerical, not fraud. A trading name on the bank account, a registered office that differs from the insurance schedule, a VAT number that belongs to a former company: each deserves a question, not a rejection.

Fields to compare every time:

• legal name (ID, registry, bank, insurance);
• company number or UTR (registry, invoice, contract);
• address (registry, insurance, invoice);
• bank account holder (bank letter, invoice);
• dates (certificate expiry, engagement start, ID expiry).

The same cross-check applies to suppliers in general; our article on vendor compliance certificate verification shows how.

What agencies and contractors ask in practice

Questions that recur in contractor and compliance communities are practical. Contractors ask whether they really need public liability insurance when they work from a laptop; most clients require it by contract regardless of the legal minimum. Agencies ask how often to refresh the file; the working rule is to re-request each document at its expiry date and at every new engagement.

A third question comes up often: do right-to-work checks apply to a contractor? Statutory right-to-work checks under the Immigration, Asylum and Nationality Act 2006 apply to employees, not to genuinely self-employed people, but many agencies still keep a record of the contractor's status as part of their file. Take advice if the arrangement is borderline.

Automating validation without removing human judgment

An agency with dozens of contractors loses most of its time retyping expiry dates and comparing company numbers between PDFs. CheckFile supports more than 3,200 document types and OCR extraction in 24 languages across 32 jurisdictions. A check compares fields (name, registration number, address, dates, account holder) across the file and against registers, then flags differences for a reviewer. It supports the decision; it does not prove by itself that a document is authentic.

Contractor files contain personal data, so keep only what you need and tell contractors how it is used, following the ICO's UK GDPR guidance. The security page describes how CheckFile handles files and the pricing page lists volumes. Our industry verification guide places these checks alongside other sectors.

To validate contractor files before each start, see the staffing and recruitment solution, which describes the completeness, validity and consistency checks applied to each file.

FAQ

What documents should a staffing agency collect from a self-employed contractor?

Collect photo ID, proof of registration (Companies House extract or HMRC UTR letter), VAT details if registered, insurance certificates, a signed contract or statement of work, and bank details in the business name. In construction, add CIS status.

How do I verify a contractor's insurance certificate?

Check the policy period, limits, insured activities and named insured, then contact the insurer or broker to confirm the policy is live. A certificate alone is a summary and does not guarantee the policy terms.

Does IR35 apply to staffing agencies?

Yes, when a worker supplies services through their own company to a medium or large client, the party that pays the worker's company, often the agency, has obligations under the off-payroll rules. The client decides status and the chain must pass the determination on.

Can an agency place a contractor as a temp worker?

No. Agency worker rules apply to people supplied to work under the client's supervision, not to independent businesses. A contractor works under a commercial contract, and mislabeling one risks tax and employment consequences.

What should I do when a contractor's documents do not match?

Ask for a written explanation and a corrected document before the start date. Name or address differences often have simple causes, but a different company number or bank account holder should pause the file until resolved.