The EU Emissions Trading System (EU-ETS) is seen as a cornerstone of the European Union's policy to combat climate change. The EU ETS works on the 'cap and trade' principle. Within the cap, companies receive or buy emission allowances which they can trade with one another as needed. After each year a company must surrender enough allowances to cover its emissions. We are currently in Phase III of the EU-ETS, which runs from 2013-2020. Phase IV of the EU-ETS, which will apply post-2020, is now being debated at EU level. So far, the European Commission has published its proposal for reviewing the Directive (July 2015). On 15 February 2017, the European Parliament adopted a report which outlines its views on the Commission's proposal and the Council adopted its general approach text on 28 February. The trilogue kicked off on 4 April.