2. The Commission shall adopt delegated acts in accordance with Article 16 to supplement this Article by laying down the necessary requirements concerning the Union registry, including rules to ensure sufficient oversight of the trading of certified units, and the factors to be considered for determining the level of fees referred to in paragraph 1 of this Article and their recovery.
During each last quarter of the year preceding the calendar year of application, the Commission shall adopt one or more implementing acts to set out or revise the individual amounts of the fees referred to in paragraph 1 of this Article to be applied for that calendar year.