Consensus means a proposal will only be adopted if all member states are in agreeance. Formal voting does not take place, the member states deliberate until they reach generaal agreement. Traditionally, this is the most used method of decision-making in the European Council.
Non-attendance: unwritten code
The European Council lacks formal rules of procedure when dealing with a possible absence of one of the member states, which by default means reaching a consensus is impossible to achieve. This will seldom pose a problem as absenteeism in the European Council is extremely low, due to the political significance of its meetings. Also, the European Council will not take highly important and/or politically sensitive decisions when one of their number is absent.
Unless otherwise indicated, this is the default 'voting method' by which the European Council takes decisions.
Consensual decision-making is based on the Treaty on European Union (TEU) and the Treaty on the functioning of the European Union (TFEU).
-application voting method: TFEU title III art. 15 paragraph 4