Tax & Employment Guide

Subcontractor vs Employee UK 2026: IR35 Three-Part Test, CIS Does Not Prove Self-Employment, Misclassification Bills Exceed £50,000

Getting worker classification wrong can cost tens of thousands of pounds. This guide explains the HMRC employment status tests, how CIS fits in, what IR35 means for your trade business, and the signs that a subcontractor may actually be a deemed employee.

Updated June 2026UK onlyConstruction & trades

Why Getting This Wrong Is Expensive

HMRC has wide powers to reclassify workers you have treated as self-employed subcontractors and determine that they were actually employees all along. When that happens, the liability lands on you as the engager — not the worker.

A reclassification typically triggers:

Backdated employer National Insurance contributions (13.8%) for every year the worker was incorrectly classified, plus interest
Backdated employee NIC and income tax that should have been deducted through PAYE
A penalty of up to 100% of the unpaid tax in cases of deliberate non-compliance
Employment tribunal claims from the worker themselves for holiday pay, sick pay and unfair dismissal rights they were never given

These are not theoretical risks. HMRC has issued enforcement notices and large retrospective bills to construction businesses, plumbers and electrical contractors across the UK. A tradesman paying three workers incorrectly for four years could easily face a liability of £50,000 or more once you add up unpaid NIC, interest and penalties.

The Construction Industry Scheme (CIS) offers no protection here. Being registered under CIS and deducting tax at source does not mean a worker is genuinely self-employed. HMRC treats the two questions — employment status and CIS compliance — as completely separate.

The HMRC Employment Status Tests

There is no single test that determines whether a worker is employed or self-employed. HMRC and the courts look at the overall picture of the working relationship, but three core tests carry the most weight.

Test 1: Control

Does the engager control what work is done, how it is done, when it is done, and where? The more control you exercise over a worker's day-to-day activities — telling them which sequence to work in, what methods to use, what time to start and finish — the more the relationship looks like employment. A genuine subcontractor decides for themselves how to carry out the work to achieve the agreed outcome.

Test 2: Substitution

Can the worker send a substitute to do the work in their place? If the answer is genuinely yes — and substitution has actually happened or is contractually permitted without your approval — that is a strong indicator of self-employment. Employment is personal service; a business can send anyone suitably qualified to fulfil the contract. If you require the specific individual to turn up every day, that points toward employment.

Test 3: Mutuality of Obligation

Is there an ongoing obligation for you to offer work and for the worker to accept it? Employees have a contract under which the employer must provide work and the employee must turn up. A genuine subcontractor has no such ongoing obligation — they quote for a specific job, complete it, invoice you, and then both parties are free. If you expect them to be available every Monday to Friday indefinitely, that mutuality of obligation points strongly toward employment.

A genuine subcontractor should comfortably pass all three tests. If even one of them is borderline, it is worth reviewing the arrangement carefully before HMRC does it for you. Additional factors the courts consider include who supplies tools and materials, whether the worker bears financial risk, and whether they work for multiple clients.

The CIS Scheme vs Employment

The Construction Industry Scheme is a tax collection mechanism, not a status determination. Under CIS, contractors deduct tax at source from payments to subcontractors — 20% if the subcontractor is registered with HMRC, or 30% if they are not — and report those deductions to HMRC each month.

This causes widespread confusion among trade business owners. Many assume that if someone is on CIS, the employment status question is settled. It is not. CIS registration simply means HMRC collects tax from that worker's earnings in advance. It says nothing about whether the working arrangement is genuinely self-employed.

HMRC has been explicit about this: a worker can be correctly registered under CIS for tax deduction purposes and simultaneously be found to be a deemed employee if their working arrangements do not reflect genuine self-employment. In that scenario you would owe employer NIC on top of the CIS deductions that have already been made, and the worker may have employment rights you have never honoured.

CIS is not a safe harbour. It is an administrative scheme you must comply with alongside — not instead of — getting employment status right.

IR35 and the Construction Industry

IR35 — formally known as the off-payroll working rules — is a separate but related set of rules aimed primarily at workers who operate through their own limited company (a personal service company, or PSC). If the work they perform would look like employment if the company did not exist, IR35 applies and the income is taxed as employment income.

From April 2021, the responsibility for assessing IR35 status shifted in medium and large businesses:

Medium and large businesses (turnover above £10.2 million, or more than 50 employees) must assess the employment status of every limited company contractor they engage and issue a Status Determination Statement (SDS). If they get it wrong, the tax liability falls on them.
Small businesses (turnover under £10.2 million, fewer than 50 employees, balance sheet under £5.1 million) are exempt from this obligation. For small trade businesses, the responsibility remains with the limited company contractor to assess their own status.

If you run a sole trader or small limited company business and you are paying a subcontractor who trades through their own limited company, IR35 is most likely their problem to manage — not yours — unless you are approaching the medium business thresholds. However, if that contractor is working in a way that looks like employment, you could still face issues under general employment status rules even if IR35 does not technically apply.

For larger construction businesses and principal contractors, IR35 due diligence on every limited company subcontractor is now a compliance obligation, not an optional extra.

Signs Your Subcontractor May Actually Be an Employee

The following patterns individually raise flags. The more of them that apply to a working relationship, the more likely HMRC will view that worker as a deemed employee:

Works exclusively for you and has done for months or years

Works the same hours every day, often dictated by you

You supply most or all of the tools, materials and equipment

You control exactly how the work is done, not just the outcome

No genuine right to send a substitute — you would reject it

Paid by the hour or day rather than by the completed job

Continuously on site with no breaks between contracts

Does not invoice you — you raise the payment yourself

Would not describe themselves as running their own business

Has no other clients and does not seek them

If several of these apply, consider taking professional advice before HMRC raises an enquiry. Voluntary correction of a misclassification before an investigation typically attracts lower penalties.

Genuine Subcontractor Arrangements

A legitimate subcontractor relationship typically has the following characteristics. The more of these that apply, the stronger your position if HMRC ever questions the arrangement:

Has their own Unique Taxpayer Reference (UTR) and is registered for Self Assessment

Works for multiple clients — you are not their only source of income

Quotes for the specific job at a fixed or agreed price

Supplies their own tools, van and specialist equipment

Has a genuine right to send a substitute if they cannot do the work

Invoices you on completion of the job

Registered under CIS with HMRC as a subcontractor

Bears their own financial risk — if they get it wrong, it costs them

Has their own public liability insurance

Decides their own working methods to deliver the agreed outcome

NIC and Tax Implications

The financial difference between employing someone and engaging a genuine subcontractor is significant. Understanding the numbers helps you see why the status question matters so much.

Employee — your obligations

Employer NIC (on earnings above threshold)13.8%
Employee NIC deducted via PAYE8–12%
Income tax via PAYE20–40%
Auto-enrolment pension (employer minimum)3%
Statutory sick pay, holiday pay obligationsYes
Employers' liability insurance requiredYes

Genuine subcontractor — your obligations

Employer NICNone
PAYE administrationNone
CIS deduction (if construction work)20% or 30%
Auto-enrolment pensionNone
Statutory sick / holiday payNone
Employers' liability insuranceNot required

Illustrative example: A worker paid £30,000 per year. As a genuine subcontractor, your total cost is £30,000 (plus CIS administration). As an employee, you would pay roughly £4,140 in employer NIC, £900 pension contributions, plus the administrative burden of payroll and the cost of statutory entitlements. The real-world difference over five years is over £25,000 — which is why HMRC treats false self-employment as a serious compliance risk.

Using the HMRC CEST Tool

HMRC offers a free online tool called Check Employment Status for Tax (CEST), available at gov.uk/guidance/check-employment-status-for-tax. It asks a series of questions about the working arrangement and returns a determination of employed, self-employed, or — in some cases — unable to determine.

HMRC has stated publicly that they will stand behind CEST results, provided you:

Answer all questions accurately and honestly
The working arrangement does not change after you run the tool
You retain a record of the result and the answers given

This makes CEST a useful defence in any HMRC enquiry. Run it before engaging any new worker, and keep a printed or saved record of the result alongside the contract. If CEST returns an “unable to determine” result, that is a signal to seek professional advice — it means the arrangement sits in disputed territory.

CEST has limitations and has been criticised by tax professionals for not always reflecting how courts approach the mutuality of obligation test. But it remains the most practical first step for trade business owners who do not have access to employment law solicitors for every engagement.

Run CEST, keep records, review regularly — especially if a subcontractor's working pattern changes over time.

Frequently Asked Questions

Can a subcontractor work exclusively for one company?

Working exclusively for one engager does not automatically make someone an employee, but it is a significant red flag that HMRC will scrutinise closely. If a subcontractor works only for you, there is no mutuality of obligation between contracts and they retain a genuine right of substitution, the arrangement may still hold up. In practice, exclusivity combined with other employment-like factors — set hours, your tools, your direction — makes reclassification highly likely. Consider whether the relationship genuinely reflects a series of independent contracts or something closer to a permanent engagement.

What happens if HMRC investigates my subcontractors?

HMRC may open a PAYE compliance review or a status enquiry. They will request contracts, timesheets, invoices and evidence of the actual working arrangements — not just what the paperwork says. If they determine workers were employees, they will raise a charge covering unpaid employer NIC, interest and potentially penalties. The charge can cover up to six years in normal cases, or up to twenty years in cases of fraud or deliberate concealment. It is worth getting ahead of any potential enquiry by reviewing your arrangements now.

Can I use a Ltd company to get round IR35?

No. Operating through a limited company does not change the underlying employment status analysis. IR35 was introduced specifically to tackle situations where workers use personal service companies to avoid employment taxes. If the working relationship looks like employment but for the existence of the limited company, IR35 applies. Paying someone through their Ltd company while they work in a way that resembles employment does not protect you — it may actually bring you within the off-payroll rules rather than the simpler self-employment rules.

What records should I keep?

Keep a copy of every subcontractor contract, the CEST result you obtained before engaging them, evidence that they have their own UTR and CIS registration, copies of their invoices, and any evidence of substitution (e.g. a different individual attending site). If you ever carry out a status review, document it and the conclusions. Good records are your first line of defence in an HMRC enquiry and can be the difference between a settled dispute and a large penalty.

Does CIS registration prove self-employment?

No. CIS registration is an HMRC administrative requirement for tax deduction in the construction industry. It is not evidence of employment status. HMRC itself has confirmed this in published guidance. A worker can be correctly registered under CIS and still be found to be a deemed employee if their actual working arrangements do not reflect genuine self-employment. CIS compliance and employment status compliance are separate obligations.

How do I pay a genuine subcontractor?

Once you are satisfied with their employment status, the process is: (1) Verify their CIS registration status with HMRC using their UTR — this determines whether you deduct 20% or 30%. (2) Receive and check their invoice. (3) Pay the invoice amount minus the CIS deduction. (4) Issue them a payment and deduction statement each month. (5) Report the payment to HMRC on your monthly CIS return. If the subcontractor is registered as a gross payment status contractor, you pay them the full invoice amount with no deduction. Keep records of all payments, deductions and verifications.

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