The coexistence of valuables and several interests in the current societies demand that the legal system will not make any movement on account of rules that have been established by one-sided only, or on account of values that are absolute. In Brazil, the Constitution that assures the right to intimacy (privacy s right), considered by the doctrine and by the jurisprudence as a ground of the bank secrecy, establishes that it is facilitated to the tax administration, specially to onfer effectiveness to the principle of the economic capacity of the taxpayers, to identify, respected the individual rights and the law terms, the assets, their incomes and their economic activities, being forbidden to attribute different treatment to those who are found under an equivalent situation. Moreover, the fact that the financial institutions are being used for illegal purposes is undeniable, serving as a way for the performance of crimes such as money laundering and foreing currency s evasion, which combat has been intensified as much as in Brazil as in the world scenery. In this process, the tension between the public interest raises, to obtain from the fiscal authority, the data that can prove the performance of illegal acts and that can provide the realization of the isonomy principles and of the tax- paying ability, as well as the protection needed of the individual private sphere, object of this present work.