The behavior of taxpayers, as a rule, corresponds to the search for an "optimal" situation to meet their needs; the behavior denotes what is objectively, observable in the taxpayer's overall reaction, regardless of what he declares, his thoughts and attitudes. This behavior, subject to taxation, may be of compliance or non-compliance with taxes, due to ethical, social, economic considerations.  Therefore, in this paper, we develop a theoretical approach to the determinants of firms' behavior, using a descriptive methodology in this respect, and we propose some solutions to increase tax compliance.