Off-payroll working, also known as "IR35," refers to a set of rules in the United Kingdom that are designed to ensure that individuals who work through personal service companies (PSCs) pay the correct amount of tax and National Insurance contributions.

Under the off-payroll working rules, individuals who provide their services through PSCs are treated as if they were employees for tax purposes unless they can demonstrate that they are genuinely self-employed. This means that they are required to pay the same tax and National Insurance contributions as employees, and their clients are required to deduct these contributions from their fees.

The off-payroll working rules apply to individuals who work through PSCs and who would be considered employees if they were directly engaged by their clients. They do not apply to genuine self-employed individuals who are in business on their own account.

If you are working through a PSC in the UK and are concerned about the off-payroll working rules and how they may affect you, it is a good idea to seek advice from a tax professional or from HM Revenue and Customs (HMRC). They can help you to understand your obligations and can provide guidance on how to comply with the rules.