This policy briefing by Reloop and Zero Waste Europe provides guidelines for legislating mixed waste sorting (MWS) in the context of the Renewable Energy Directive (RED). The guidelines were developed to clarify the amendment proposed by the European Parliament regarding the use of mixed wastes for ‘renewable energy’ purposes. The document recommends applying MWS systems of defined quality to remove fossil-derived materials to ensure that only biogenic waste is used for renewable energy generation. Following the requirement, the operators would either need to pre-sort the waste on-site or demonstrate that all waste received has undergone sorting prior to it being delivered for incineration.