This topic is of great importance, as the principle of equality has not only been confirmed by constitutional documents, but divine laws and international conventions have also recognized this principle, which makes It deserves attention, especially in the field of taxation. The principle of equality before taxes is of great importance from both constitutional and financial perspectives. From a constitutional perspective, this principle is considered a basic guarantee for taxpayers in the face of the legislator and the tax administration. If either of these two parties violates this rule, taxpayers have the right to force the violating party to respect its constitutional obligations. From a financial perspective, guaranteeing the principle enhances taxpayers' sense of satisfaction and belief in justice, which prompts them to pay taxes in full and without hesitation. On the other hand, arbitrary discrimination between them can lead to a feeling of resentment and injustice, and negatively affect tax justice, which may cause an increase in cases of tax evasion that cause great harm to the public treasury. We will discuss this topic within the framework of two sections. In the first section, we will explain the concept of the principle of equality before tax, and in the second section, we will discuss the requirements of the principle and the exceptions to it.