of this Article must be established and estimated and a deadline set, which may not be shorter than 15 days or longer than two months, by which the liable entities referred to in the first paragraph of this Article may submit their opinions, remarks and proposals regarding the planned issuing or amendment of the tariff. Discussions may also take place at this time between the relevant parties. Article 7 (setting and payment of fees) (1) The fee referred to in the preceding paragraph shall be set by the Agency in a decision setting the fee. (2) Fees shall be set in advance for the current calendar year. (3) In the first calendar year in which the obligation to pay a fee arises, the Agency shall set the fee as one-twelfth of the annual fee multiplied by the number of months remaining from the occurrence of the liability to the end of the year. However, it may not amount to less than one-twelfth of the annual fee. (4) An entity liable to pay a fee for the calendar year in which it ceases the provision of a public communications network and/or public communications service shall pay the fee on the basis of the number of months in which it provided the public communications network and/or public communications service, but not less than one-twelfth of the annual fee. The Agency shall, at the request of the liable entity, amend a decision setting the fee that has already been issued and return any advance payment to the liable entity within 30 days of delivery of the amended decision setting the fee. Article 8 (supervision) The Agency shall oversee the implementation of the provisions of this Chapter. III. CONSTRUCTION OF NETWORKS AND ASSOCIATED INFRASTRUCTURE Article 9 (spatial planning, construction and maintenance) (1) For the purposes of spatial planning, a public communications network and associated infrastructure shall be considered commercial public infrastructure. (2) The construction of public communications networks and associated infrastructure, the construction of electronic communications networks and associated infrastructure for the requirements of security, the police, defence, and protection, rescue and relief, and the construction of other electronic communications networks and associated infrastructure on, over or under real estate owned by entities of public law shall be deemed to be for the public benefit. (3) The maintenance of communications facilities which are part of the networks and associated infrastructure referred to in the preceding paragraph shall be deemed to be maintenance work for the public benefit within the meaning of construction regulations even if they are not intended for the provision of a commercial public service. The following shall be deemed to be maintenance work for the public benefit on communications facilities: 1. the completion and upgrading of existing communications facilities or equipment of electronic communications networks (e.g. installation or replacement of equipment, including the replacement of overhead cable supports, increasing of capacity, installation of