Thousands of UK companies may be breaking the rules when it comes to reviewing the status of the freelance contractors who work for them, a tax and advisory firm has warned.

Companies have been required to assess whether each contractor is working in a pattern which is “akin to that of an employee” unless they are exempt from the IR35 requirements as small businesses since April this year.

Businesses are also legally obliged to account for PAYE and NICs on the invoices ...