The ‘tax gap’ figures for 2012/13 show that illegal activity is costing the UK almost five times as much as tax avoidance. Whereas tax evasion is contrary to law, tax avoidance is not; therefore it can be difficult to determine whether a particular form of tax avoidance is acceptable. Avoidance opportunities arise where the ramifications of a particular tax policy or provision have not been fully considered. Cross-border arbitrage also creates scope for avoidance. Greater co-operation between tax authorities and the BEPS action plans should reduce opportunities in that area. However, adverse publicity and the desire to maintain a good working relationship with HMRC are the most powerful drivers in reducing avoidance.