Commission Delegated Regulation (EU) No. 666/2014 establishing substantive requirements for a Union inventory system and taking into account changes in the global warming potentials and internationally agreed inventory guidelines pursuant to Regulation (EU) No. 525/2013 of the European Parliament and of the Council.

This Regulation defines the requirements for a European Union inventory system and sets forth rules on the preparation and administration of the Union greenhouse gas inventory, including rules on cooperation with the Member States during the annual reporting process and the United Nations Framework Convention on Climate Change (UNFCCC) inventory review. The Union greenhouse gas inventory is the sum of Member States' greenhouse gas emissions from sources and removals by sinks for the territory of the European Union in accordance with article 52 of the Treaty on European Union and is established on the basis of the Member States' greenhouse gas inventories, as reported pursuant to article 7 of Regulation (EU) No. 525/2013.
In addition, this Regulation lays down rules with regard to the global warming potential values and the internationally agreed inventory guidelines to be used by the Member States and the Commission in the determination and reporting of the greenhouse gas inventory.