“Authorisation” is a new but as yet undefined component of the guidance for implementation of Article 6 of the Paris Agreement. Authorisation is important as it triggers both corresponding adjustments and reporting requirements. This paper identifies and analyses open questions related to what is authorised, by what process, for what purpose, the format and timing of authorisation, and how any ex-post changes to authorisation can be made. The answers to these questions can affect the attractiveness for Parties and the private sector to participate in Article 6 cooperation. The paper also outlines areas of Article 6.2 guidance that could be usefully clarified at the international level, and implications of different options for the domestic implementation of Article 6 authorisation provisions, drawing from examples of a few frontrunner Parties who have already established bilateral agreements and domestic structures for international cooperation under Article 6. The paper concludes that some of the open questions could be clarified at the international level, such as how to report any changes to authorisations and if the authorisation needs to be provided concurrently by the participating Parties. Other questions could be clarified at the national level by the participating Parties providing the authorisation. These include whether participating Parties can choose to include additional elements in their authorisations, and which roles authorised entities could play.