At the center of this paper is the European Union, its history, extensions and common policies that have existed for many years. The beginnings of the European Union are tied to the end of the Second World War to establish peace and co-operation between the warring countries. Through its history, the desires of the Union have grown and so the expansion of the Union began. So far, the European Union has had seven extensions. The paper describes the common policy of the European Union and is mostly based on the monetary policy of the European Union which has a specific strategy to implement it, who carries out that policy and which are its instruments and aggregates. Monetary policy is divided into expansive and fiscal policies that are achieved by various instruments. Aggregates in monetary policy are M1, M2 and M3 aggregates. Monetary policy of the European Union is carried out by the European Central Bank. The paper discusses the European Monetary Union as well. The Monetary Union represents countries that have a common euro currency. In order for a country to enter the monetary union, a number of strict criteria must be met. In the currency is divided into banknotes and coins of the euro. All EU Member States have a common budget from which they can withdraw funds to implement various projects, which the states are unable to finance from their own budgets