The Single European Act is in Effect.

Although import duties between member states were abolished in 1968, trade is not free between Community countries due to differences in national legislation. The Single European Act establishes a six-year program to eliminate these differences, while also strengthening the role of the European Parliament and formalizing the name “European Parliament.”
The Single European Act sets the goal of creating a single market by removing barriers and harmonizing standards.
It introduces the cooperation and assent procedures, giving the Parliament a say in legislation for the first time.
It initiates cooperation in foreign policy and extends the use of qualified majority voting for decision-making within the Council.
The Single European Act provides a legal basis for the European Council, while the Summits of Heads of State and Government are formalized.