in compliance with the cost accounting rules laid down by the Communications Regulatory Authority. The Communications Regulatory Authority shall have the right to establish a cost accounting system, methodology and/or model to be used by an operator or operators having significant market power on the relevant market. Such accounting system, method, and/or model, the Communications Regulatory Authority is required to publish on its website. Compliance with cost accounting rules and other legal acts as well as with the cost accounting system, methodology and/or model prepared by the operator and/or established by the Communications Regulatory Authority must be verified by an audit. The audit opinion must be published annually in accordance with the rules established by the Communications Regulatory Authority. Article 231. Obligation of functional separation 1. Under exceptional circumstances (when the Communications Regulatory Authority identifies that the obligations imposed by the Article 18, 19, 20, 21, 22 and 23 are not sufficient to ensure effective competition and where important and persisting competition problems on the market relating to access provision occur), the Communications Regulatory Authority shall, with regard to Article 17(4) of this Law, have the right to oblige a vertically integrated undertaking to separate its relevant wholesale access services from the rest of the undertaking's activities, by transferring it to a separate legal entity. 2. An undertaking, which has the functional separation obligation, shall provide access to all undertakings, including subsidiaries of a vertically integrated undertaking referred to in paragraph 1 of this Article, on the same terms and conditions, including the price and quality of services, and using the same systems and processes. 3. The Communications Regulatory Authority shall notify the European Commission about their intention to establish a functional separation obligation stating: 1) the grounds on which imposition of the obligation referred to in paragraph 1 of this Article are based; 2) a grounded assessment that effective and long-term competition will not arise in the electronic communications infrastructure within a reasonable period of time or it will not be sufficiently effective; 3) the expected impact on the Communications Regulatory Authority, on the undertaking which is imposed the obligation referred to in paragraph 1 of this Article, particularly on the employees of the undertaking, and the entire electronic communications 40