Article 19 3.

The Commission is empowered to adopt delegated acts in accordance with Article 23 to supplement this Directive by laying down all necessary requirements concerning the Union Registry for the trading period commencing on 1 January 2013 and subsequent periods, in the form of standardised electronic databases containing common data elements to track the issue, holding, transfer and cancellation, as applicable, of allowances, and to provide for public access and confidentiality, as appropriate. Those delegated acts shall also include provisions to put into effect rules on the mutual recognition of allowances in agreements to link emission trading systems.