Member States or any competent authority they designate, including the regulatory authorities referred to in Article 39(1) and the dispute settlement authorities referred to in Article 34(3), shall, insofar as necessary to carry out their functions, have right of access to the accounts of natural gas undertakings as set out in Article 31.

Member States and any designated competent authority, including the regulatory authorities referred to in Article 39(1) and the dispute settlement authorities, shall preserve the confidentiality of commercially sensitive information. Member States may provide for the disclosure of such information where this is necessary in order for the competent authorities to carry out their functions.

Member States shall take the necessary steps to ensure that the accounts of natural gas undertakings are kept in accordance with paragraphs 2 to 5 of this Article. Where natural gas undertakings benefit from a derogation from this provision on the basis of Article 49(2) and (4), they shall at least keep their internal accounts in accordance with this Article.

Natural gas undertakings, whatever their system of ownership or legal form, shall draw up, submit to audit and publish their annual accounts in accordance with the rules of national law concerning the annual accounts of limited liability companies adopted pursuant to the Fourth Council Directive 78/660/EEC of 25 July 1978 based on Article 44(2)(g)19 of the Treaty on the annual accounts of certain types of companies20.

Undertakings which are not legally obliged to publish their annual accounts shall keep a copy thereof at the disposal of the public at their head office.

Natural gas undertakings shall, in their internal accounting, keep separate accounts for each of their transmission, distribution, LNG and storage activities as they would be required to do if the activities in question were carried out by separate undertakings, with a view to avoiding discrimination, cross-subsidisation and distortion of competition. They shall also keep accounts, which may be consolidated, for other gas activities not relating to transmission, distribution, LNG and storage. Until 1 July 2007, they shall keep separate accounts for supply activities for eligible customers and supply activities for non-eligible customers. Revenue from ownership of the transmission or distribution network shall be specified in the accounts. Where appropriate, they shall keep consolidated accounts for other, non-gas activities. The internal accounts shall include a balance sheet and a profit and loss account for each activity.

The audit, referred to in paragraph 2, shall, in particular, verify that the obligation to avoid discrimination and cross-subsidies referred to in paragraph 3 is respected.

Undertakings shall specify in their internal accounting the rules for the allocation of assets and liabilities, expenditure and income as well as for depreciation, without prejudice to nationally applicable accounting rules, which they follow in drawing up the separate accounts referred to in paragraph 3. Those internal rules may be amended only in exceptional cases. Such amendments shall be mentioned and duly substantiated.

The annual accounts shall indicate in notes any transaction of a certain size conducted with related undertakings.