Understanding IR35 status is important for contractors, recruitment agencies and businesses that engage individuals through personal service companies. The rules can affect how income is taxed, who is responsible for making employment status decisions and whether tax deductions need to be made through PAYE.

For contractors working in the UK, checking IR35 status before starting an assignment can help clarify the tax treatment of an engagement and reduce the risk of unexpected problems later. Businesses also need to understand their responsibilities when hiring contractors through intermediaries.

In this guide, we explain how to check IR35 status, which factors influence the assessment, who is responsible for making status decisions and how contractors and businesses can approach the process more effectively.

What Is IR35?

IR35 is the commonly used name for UK tax rules that apply to certain individuals who provide services through an intermediary, such as a personal service company.

The rules aim to determine whether an engagement would be treated as employment for tax purposes if the intermediary were not involved.

If an engagement falls inside IR35, the relevant payment arrangements generally need to account for employment taxes under the applicable rules. If an engagement falls outside IR35, payments may be made without employment taxes being deducted under those rules, although other tax and legal responsibilities may still apply.

IR35 does not mean that every contractor is automatically treated as an employee. Each engagement must be assessed according to its particular circumstances.

The assessment should focus on the actual working arrangements, rather than relying only on the contract's title or the fact that a contractor operates through a limited company.

Why Should You Check IR35 Status?

Checking IR35 status helps contractors and businesses understand the potential tax treatment of an assignment before work begins.

Understanding Tax Responsibilities

An IR35 assessment can help establish whether an engagement is likely to be treated as employment for tax purposes.

This matters because the applicable rules may affect how payments are processed and who must account for Income Tax and National Insurance contributions.

Avoiding Unexpected Deductions

Contractors who understand their engagement's tax treatment can make more informed financial plans.

If an engagement is determined to fall inside IR35, the payment arrangement may involve PAYE deductions. Understanding this in advance can help contractors assess the financial implications of accepting an assignment.

Supporting Business Compliance

Businesses engaging contractors through intermediaries may have legal responsibilities for determining employment status and communicating the outcome.

A documented assessment can help demonstrate how the decision was reached and support a more organised compliance process.

Making Better Contracting Decisions

Understanding IR35 status before accepting work allows contractors to ask relevant questions about the contract, working arrangements and payment structure.

This can reduce misunderstandings between contractors, agencies and clients.

How to Check IR35 Status in the UK

There is no single factor that determines every IR35 decision. A reliable assessment considers the overall working relationship and the relevant legal principles.

Step 1: Review the Contract

Start by examining the written contract between the parties.

Look at the services being provided, payment terms, responsibilities, working arrangements and provisions relating to substitution or termination.

However, the written contract is only part of the picture. The actual working practices must also be considered.

If the contract describes an independent arrangement but the working relationship operates differently, the real circumstances may carry significant weight.

Step 2: Consider Control

Control is an important factor in employment status assessments.

Consider who decides how, when and where the work is completed. A client may specify the required outcome without controlling every aspect of how the contractor delivers it.

The level of control can vary considerably between assignments.

For example, a specialist consultant who decides how to complete a defined project may have a different working arrangement from an individual who works under detailed day-to-day direction.

Control must be considered alongside the other relevant factors rather than used as the sole basis for a decision.

Step 3: Examine Substitution Rights

The right to provide a suitably qualified substitute may be relevant to the assessment.

Consider whether the contract permits substitution, whether the right is genuine and whether the working practices support it.

A clause that exists only on paper may carry limited weight if substitution is not genuinely possible in practice.

The assessment should reflect the real obligations and arrangements between the parties.

Step 4: Assess Mutuality of Obligation

Mutuality of obligation is another factor considered in employment status cases.

The assessment may examine what the parties are required to provide or accept, including whether the client must offer work and whether the individual must accept it.

The nature of these obligations can differ between assignments.

It is important to consider the relationship as a whole rather than assume that one contractual term determines the IR35 outcome.

Step 5: Review Financial Risk

Financial risk can help indicate whether an individual is operating independently.

Consider whether the contractor is responsible for correcting defective work, bears certain business expenses or may incur additional costs when delivering the agreed service.

A contractor who genuinely bears business risks may have a different relationship from someone who receives payment in a way closely resembling an employee.

Financial risk is one part of the overall assessment and should not be considered in isolation.

Step 6: Compare the Contract With Actual Working Practices

After reviewing the contract, compare its terms with how the assignment operates in practice.

Check whether the contractor works independently, whether substitution is genuinely available and how responsibilities are managed.

Any significant differences between the contract and working practices should be investigated.

A robust assessment should be based on accurate information and should be reviewed if the working arrangements change materially.

Who Is Responsible for Checking IR35 Status?

Responsibility depends on the type of engagement and the parties involved.

For many public sector engagements and medium or large private sector clients, the client is generally responsible for determining employment status for tax purposes and issuing a Status Determination Statement, subject to applicable exceptions.

The determination should explain the conclusion and provide reasons.

Where the relevant rules apply, the client must communicate the determination to the worker and the party it contracts with directly. Responsibility for operating PAYE may fall on the fee payer or another party in the payment chain, depending on the circumstances and statutory rules.

For engagements with qualifying small private sector clients, responsibility generally remains with the worker's intermediary, although the applicable rules and exceptions should be checked.

Contractors should not assume that every client has identical responsibilities. The size and status of the client, the sector involved and the engagement structure can affect the position.

Businesses should consult current HMRC guidance or obtain professional advice if they are uncertain about their obligations.

What Is HMRC's CEST Tool?

HMRC provides the Check Employment Status for Tax tool, commonly known as CEST.

The tool asks questions about the working arrangement and uses the answers to help assess employment status for tax purposes.

It can be useful for clients, contractors and other parties involved in an engagement. However, the quality of the result depends on the accuracy and completeness of the information entered.

Users should answer questions carefully and avoid choosing responses simply because they produce a preferred outcome.

Where the tool cannot determine the status or the circumstances are particularly complex, further professional advice may be appropriate.

You can access the tool through the official GOV.UK website by searching for Check Employment Status for Tax.

Common IR35 Status Checking Mistakes

Contractors and businesses can make mistakes when assessing employment status. Recognising these problems can improve the process.

Relying Only on Contract Wording

A contract may describe an individual as self-employed, but this does not automatically establish the tax status of the engagement.

Actual working practices must be considered alongside the written terms.

Ignoring Changes to Working Arrangements

An assignment may change after it begins. New responsibilities, different levels of supervision or changes to the working relationship may affect the original assessment.

Businesses should review status when material changes occur.

Using an Online Tool Without Understanding the Questions

Online tools can help organise information, but they do not remove the need to provide accurate answers.

Users should understand the arrangement and seek additional advice where necessary.

Treating Every Contractor the Same Way

Different contractors may have different responsibilities, levels of independence and contractual arrangements.

Each engagement should be assessed on its own facts.

Failing to Document the Decision

Keeping a record of the information considered, the reasoning behind the conclusion and the final determination can support transparency and future reviews.

How The Infinity Group Can Support Your Business

The Infinity Group provides business support for organisations exploring ways to manage their financial and administrative responsibilities.

Businesses reviewing IR35 requirements should identify their engagement structures, contractual arrangements and responsibilities before deciding what support they need.

Before proceeding, confirm whether the specific IR35 assessment or compliance support you require is available. For complex status questions, businesses and contractors may need advice from a suitably qualified tax or employment status specialist.

Final Thoughts

Checking IR35 status is an important step for UK contractors and businesses that engage individuals through intermediaries.

A reliable assessment considers the contract, control, substitution, mutual obligations, financial risk and actual working practices. No single factor should automatically determine the result.

Businesses should also understand who is responsible for making the determination, communicating it and operating payroll where required.

By reviewing each engagement carefully, keeping appropriate records and seeking professional advice when necessary, contractors and businesses can make better-informed decisions about IR35 and their tax responsibilities.