The IR35 rules are designed to prevent the avoidance of tax and NICs by the use of an intermediary company owned by the "employee". The Coalition Agreement promised a review of these complex rules with a view to replacing it "with simpler measures that prevent tax avoidance but do not place undue administrative burdens or uncertainty on the self-employed, or restrict labour market flexibility."
The HM Treasury Budget Report confirms the Governments commitment to a review of IR35 and small business tax and will release further details shortly.