Methods of estimating income tax are important matters for any tax system that seeks to achieve tax justice for the taxpayer in the tax accounting process on the one hand, while ensuring access to the taxpayer's real income from sources of income on the other hand, and thus obtaining the actual tax amount achieved on the taxpayer, and there are several types of Methods of estimating income tax in Iraqi tax legislation, and this research deals with the method of reserve estimation of income, which is one of the common methods used in departments of the General Tax Authority to the point of exaggeration in its misplaced use in the Income Tax Law 113 of 1982 and its effective amendments. The research is a method of studying the case of reserve assessment that is used in many types of income estimation in the General Tax Authority, which are not consistent with what is stated in the Income Tax Law regarding the use of the method of reserve assessment for estimating income tax, with the application examples that illustrate this, and the research touched a set of conclusions One of them is that the precautionary assessment is practiced incorrectly in the tax departments, and there is confusion about that, as what these departments consider as a precautionary estimate is in fact true The time of a preliminary assessment, in addition to that the reserve assessment is not subject to appeal by the taxpayer because the tax appeal is required to respond to final decisions and not just a decision that has a temporary procedural nature and does not create fixed rights or obligations, as the researcher reached a set of recommendations through which it can be Addressing the defect in the applications of this method when estimating the income tax.