The analysis of jurisdiction of national supreme courts as well as jurisdiction of European Court of Justice allows to state that two main approaches - conservative and modern (evolutionary) - have appeared. The latter is especially noteworthy. It creates new tax law institutions in accordance with requirements of a democratic state ruled by law. The modern approach (trend) is a source of two interesting tax law institutions; the first is known as the agreement between the taxpayer and tax administration and the second is the institution of conditional unlimited tax duty. The former, which is a particular type of a public law agreement, has been created by jurisdiction of German Supreme Court of Financial Law (Bundesfinanzhof), while the latter one - by jurisdiction of European Court of Justice and it has been implemented in tax law systems of the EU members.