Taxes are an instrument for collecting state revenues from which public expenditures are financed, ie they are used for the purpose of meeting public needs. Tax Administration (here in after: PU) is organized within the MFIN, so according to the Tax Administration Act (NN 115/16, 98/19) the tasks performed by MFIN-PU are as follows: determining the timeliness, legality and regularity of submitted tax returns, receiving returns, recording liabilities in tax accounting collection and refund of taxes, contributions, detection, prevention and suppression of tax fraud and tax offenses. Also, the PA can perform the tasks of recording, control and collection of revenues for local self-government units, revenues of social other public benefits and other benefits prescribed by law. This paper presents the business process of Control over the implementation of sales fiscalization through self-service devices, and the aim of this paper is to show how the Tax Administration works, what is its purpose and activities to prevent the gray economy, and protect the state budget and taxpayers. Fiscalization is according to the Law on Fiscalization (NN 133/12, 115/16, 106/18, 121/19, 138/20) a set of measures implemented by taxpayers, in order to enable efficient monitoring of cash transactions. It is carried out by computer connection to the Internet system of the PU of the Republic of Croatia.