With the Turkish Commercial Code No. 6102 (6102 TCC), internal auditing system, which is not based on expertise, has been abolished and the external auditing system has been adopted for capital companies. Thus, audit of a company has turned into accounting control. In this study, the auditing of the capital companies was examined within the scope of the auditing organisations and the companies subject to the audit. Capital companies are classified as those subject to independent audit and those subject to auditor audit. In this context, the independent auditor may only be an independent auditor or an independent auditing company. The implementation of TMS (Turkish Accounting Standards) is compulsory for some of the companies, which are subject to independent auditing, whereas it has been left at the discretion of the company for the others. Companies that do not have an obligation to implement the TMS will be able to apply TMS or continue to implement a uniform accounting system. The auditor explains the result of the audit in the opinion letter. Opinion letters can be positive, limited positive and refraining from giving an opinion or negative opinion. Provisions related to the liability arising from the audit are included in the Decree Law numbered 660 and in the audit regulation. In addition, the responsibility of the auditors arising from the confidentiality obligation has been particularly regulated in the TCC.