I truth

clarity and certainty

Clarity and certainty (one of Adam Smith's 4 principles) 
The application of a tax should be clear and certain. This principle, considered very important by Smith, has often been underestimated in modern tax systems (in which open and impartial administration usually can be taken for granted). In nations where the application of taxes is uncertain and arbitrary, however, the public can have no confidence in the system. Even in the U.S., high rates of inflation have sometimes created fears and uncertainties about rising tax bills and the fairness of imposing taxes on inflated values. Such reactions demonstrate the importance of clarity and certainty as principles of a respected tax system. (FW)