According to 2003/55/EC Article 19, in the case of negotiated access, Member States shall take the necessary measures for natural gas undertakings and eligible customers either inside or outside the territory covered by the interconnected system to be able to negotiate access to storage and linepack, when technically and/or economically necessary for providing efficient access to the system, as well as for the organisation of access to other ancillary services.
Member States shall require storage system operators and natural gas undertakings to publish their main commercial conditions for the use of storage, linepack and other ancillary services.