A Guarantee of Origin (GO or GoO) is an energy certificate defined in article 19 of the European Directive 2018/2001/EC ( previously in article 15 of the European Directive 2009/28/EC). A GO certifies attributes of electricity, gas (including hydrogen), heating and cooling, especially coming from renewable sources and provides information to energy customers on the source of their energy. Guarantees of Origin are the only defined instruments evidencing the origin of electricity generated from renewable energy sources.