Following the global financial crisis the amount of money owed to revenue bodies increased sharply and it still has not fallen back to pre-crisis levels. It is estimated that OECD-governments alone were owed around two thirds of a trillion US dollars in undisputed tax debts at the end of 2013. For FTA member countries the total value of the tax debt book averages more than 12% of total net revenues, or more than six weeks’ worth of tax income. In some countries it is even larger. As governments work to repair public finances they expect revenue bodies to improve the flow of tax income and reduce their costs. Ensuring that everyone pays his or her taxes is also vital in terms of the perceived fairness of the tax system.