Firms will have to centrally clear certain classes of interest rate swaps starting from 21 June 2016. The clearing obligation in the Europe Union (EU) will enter into force following the publication of the relevant technical standards in the Official Journal on 1 December 2015.
More info via press release: http://www.esma.europa.eu/news/Press-release-European-swap-clearing-start-June-2016?t=326&o=home