IR35 extended to private sector Philip Hammond’s decision to extend the IR35 system from the public to the private sector could bring in over £1bn in tax revenue in its first year. Large and medium-sized companies will have to review all their contracts with freelance staff and determine whether they should be taxed under IR35 rules. The move, which will come into effect from April 2020, has been described by accounting experts as “one of the most significant changes to the operation of employment taxes for many years” which will “put a significant burden on business at a time when contingency planning for Brexit is already stretching resources”. Businesses in the construction and manufacturing sectors are among those most likely to be impacted.