All large enterprises as defined in Article 3, Paragraph 22 of the Law on Energy Efficiency are obliged to carry out an energy audit every four years, in accordance with the provisions stipulated in this Law and the Rulebook on Energy Audits of Large Enterprises. Large enterprises are not obliged to carry out external energy audits in cases when they have implemented an energy management system certified by a conformity assessment body accredited in accordance with the Law on Accreditation, which is compliant with the relevant European or International Standards (ISO), provided that the management system includes an internal energy audit that meets the detailed conditions prescribed in the Rulebook on Energy Audits of the Large Enterprises.