Understanding IR35: A Comprehensive Guide for Contractors and Businesses

"Mastering IR35: A Complete Resource for Contractors & Businesses"

Understanding IR35: A Comprehensive Guide for Contractors and Businesses

IR35 is a term used to describe a set of tax rules that were introduced in the UK in 2000 to prevent tax avoidance by workers who, in the view of HM Revenue & Customs (HMRC), were effectively employees but were providing their services through their own limited companies, known as personal service companies (PSCs).

Belonging to a PSC can provide tax savings to workers, but they are not entitled to the same employment rights as traditional employees. The IR35 rules aim to ensure that workers who should be classified as employees pay the same amount of tax and National Insurance contributions as salaried workers do.

Implications for Contractors and Businesses

If you are a contractor working through a PSC, it is your responsibility to determine whether your assignment falls inside or outside of IR35.

If it falls within IR35, your PSC payment should be treated as salary, and you will be taxed and pay National Insurance Contributions accordingly.

If you are a business that hires contractors, it is important to be aware of IR35 rules so that you don't inadvertently breach them.

If you are assessed to be inside IR35, you will be responsible for paying the relevant employer's National Insurance Contributions, which can be a significant hidden cost for businesses. Therefore, it is crucial to understand the IR35 status of contractors and make sure that you are compliant with the regulations.

Determining IR35 Status

The first step in determining your IR35 status is to carry out a status check. This will determine whether your assignment is similar to that of an employee or a self-employed contractor.

To determine your IR35 status, HMRC considers a range of factors, including:

  • The degree of control over how the work is carried out
  • The level of integration into the client's business
  • Mutuality of obligation (whether the client is obliged to offer work and the contractor is obliged to accept it)
  • Whether the contractor can provide a substitute to do the work
  • The financial risk of the assignment

It is important to note that IR35 status can vary between assignments. Just because one assignment is deemed to be outside of IR35 does not mean that all assignments will be.

Compliance with IR35

Contractors and businesses can take steps to ensure compliance with IR35. These include:

  • Clarifying the terms of the assignment and the working relationship between the client and the contractor in a clear, written agreement
  • Conducting regular IR35 status assessments and updating them as needed
  • Ensuring that the contractor has the right to provide a substitute to carry out the work
  • Avoiding any clauses or stipulations that would indicate an employment relationship
  • Ensuring that the contractor bears a certain level of financial risk and is responsible for providing their own tools and equipment


The IR35 regulations are an important aspect of the UK's tax system, and failure to comply with them can result in serious consequences for contractors and businesses alike. To avoid unexpected tax bills or legal disputes, it is crucial to understand your IR35 status and take appropriate steps to ensure compliance. By clarifying the terms of your working relationship and regularly assessing your IR35 status, you can minimise the risk of misclassification and protect your finances and reputation.