Abstract: The research subject is the analysis of reasons for gaining tax benefit by tax payers as assessed by commercial courts. The authors consider the alternative positions of both the supporters of formalization of the signs of an unfounded tax benefit in the Tax Code of the Russian Federation, and those who think that the formation of law enforcement approaches to this problem can replace the source of law establishing the criteria of negligence and the lack of due prudence. The authors study the circumstances, which can lead to the classification of a benefit as unfounded, and the facts, which, considered individually (without an account for other circumstances), cannot speak for the absence of reasons for a tax benefit. Special attention is given to the problem of the absence of a mechanism of prevention of abuse of rights for the purpose of taxes minimization and obtaining an unfounded tax benefit in the Russian legislation on taxation and revenue. The authors conclude it is impossible to foresee a comprehensive list of criteria, but the legislation must contain a general idea of deliberate acts aimed at unfounded gaining of tax benefit.