Tax avoidance is a phenomenon faced by all countries, to a lesser or greater extent, and we can say that it has begun to manifest itself since the introduction of taxes. It is known that generally taxes are not pleasing to taxpayers, especially when their level is high. However, it is important for individuals, as a whole, not to evade from their tax obligations. In this context taxes can be regarded as a necessary evil to ensure the resources needed for state functioning. But often some taxpayers are looking for ways to avoid taxes, engaging either in tax evasion to the shelter of the law or in fraudulent evasion. In this paper we present some of the aspects that motivate individuals to pay taxes. Also we analyze the situation of budgetary revenues in Alba County and also the evolution of the main income of consolidated general budget in Romania. In the end of the paper we intend to draw a parallel between shadow economy, tax burden and tax losses due to shadow economy for a sample of 32 countries. In this way we can see where underground economy and tax losses have the highest values and where are required measures to mitigate them.