IR35 rules are intended to combat tax avoidance by contractors who are effectively operating as employees while benefiting from the self-employed tax regime. Contractors who fall clearly outside IR35 are deemed self-employed by HMRC and are able to pay lower overall levels of tax and National Insurance Contributions. IR35 contractors who fall within the HMRC off-payroll rules must pay tax and national insurance on the same basis as any other employee performing their role.