The audit market, developed out of the need to strengthen the credibility and the quality of financial reporting, has led since the 1980s to a concentration around large audit firms, the dominance effect being marked on the one hand by the auditor's increasing reputation and notoriety, and on the other hand by the client's association with a reputed auditor, which contributes to improving the company's image on the market. In this context, a major issue is represented by the level of the fees

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... arged, as they represent key elements that may affect the auditor's independence. Moreover, a sensitive aspect is the relationship between the fee charged for financial audit services and the one for non-audit services and the compensation practices between them. The European Commission wants to facilitate competition in an overly concentrated market and also provide the opportunity for small and medium-sized audit firms to become active players in the large corporate audit market through joint audit, in which at least one of the audit firms is not part of the Big4 group. The mandatory audit firm rotation and the limitation on the non-audit services provided are the main aspects of the recent audit reform that directly influences the fee level. The main purpose of this study is to analyse whether there is a pattern of audit costs at the community level. In this context, this paper aims to assess the uniformity of audit costs, namely to determine the structure of the audit market in the European Union. The research involves data set comparison methods, by analysing a sample of 2,896 firms listed on the stock exchange in 35 different states over the period 2013-2021.