Euro 4 has been in place since January 2016.
Euro 5 will be introduced on 1 January 2020 for new type-approval (and 1 January 2021 for all new vehicles) except for micro-cars (L6e-B), three-wheel mopeds designed for utility purposes (L2e-U), trial (L3e-AxT) and enduro (L3e-AxE) motorcycles which benefit from a 4-year additional leadtime.
Current EU Legislation
Regulation (EU) No 168/2013 of the European Parliament and of the Council of 15 January 2013 on the approval and market surveillance of two- or three-wheel vehicles and quadricycles
Commission Implementing Regulation (EU) No 901/2014 of 18 July 2014 with regard to the administrative requirements
Commission Delegated Regulation (EU) No 134/2014 of 16 December 2013 with regard to environmental and propulsion unit performance requirements