Taxes are one of the most important forms of public revenues for countries, as their theory has great importance among the theories used in public finance. It is also characterized by its important role in contributing to achieving the goals of fiscal policy. Therefore, many concepts and definitions related to taxes have emerged. They are known as mandatory assignments determined by countries. Individuals are obligated to pay its value free of charge in order to provide assistance to countries in achieving societal goals.

Among its other definitions, it is a contribution of a cash or in-kind nature, which individuals provide to the countries in which they live, whether they receive a benefit from public services or not, and countries impose these taxes because they are linked to economic, political, and financial goals.
Taxes witnessed a development in economic thought in conjunction with the emergence of many economic intellectual stages. The following is information about the most important of them:

- Taxes in Physiocratic Economic Thought:
It is an intellectual field that appeared in the eighteenth century AD in France, and thinkers of this economy were interested in unified taxes imposed on agricultural lands, as it is the only source of wealth provision, and the owners of these lands are the social group that produces a net revenue, so there is no point in imposing taxes on the owners of other classes.

- Taxes in Classical Economic Thought:
This thought focused on the need to achieve a balance between estimates of public revenues and public expenditures, as the best financial management depends on having a balance in the budget, and avoiding any risk of the emergence of a deficit in it. At this intellectual stage, a group of tax ideas appeared among several economic thinkers, the most important of which are:

*Taxes according to Adam Smith:
Where he was keen to identify four bases for tax, which included collection, appropriate collection, certainty, and justice, and Smith pointed out the necessity of the need for taxes, because they are one of the main means of financing for countries.
*Taxes according to David Ricardo:
Where he saw that the industrial, agricultural, and commercial sectors should stay away from the intervention of states, but when countries want to meet their own expenses, they must deduct the value of these taxes, as Ricardo considers it a type of rent for real estate that affects the real estate price, and does not affect the price of real estate. consumer.

There are several types of taxes, and each of them has its own field, the most important of which are:
- Taxes on persons:
It is one of the oldest types of taxes known since the Middle Ages, as it was imposed on all individuals, and it is distinguished by its ease of calculation, collection and imposition.
- Taxes on money:
It is imposed on all the money of an individual, and is characterized by justice and abundance, but it is not possible to limit all the properties of individuals, which leads to encouraging them to evade tax.

- Direct and indirect taxes:
They are the common and widespread taxes in the modern era, but it is difficult to differentiate between them, so it is relied on using a set of criteria to compare these taxes, namely:
*The stability of the taxable service or product:
They are all items on which taxes are imposed. If they are permanently fixed, they are considered direct taxes, but if they are not fixed, they are considered indirect taxes.

*Acquisition Standard:
It is based on the nature of the administrative body that collects taxes or the method used to collect them, and this criterion varies between countries of the world.
*Transferring the burden of taxes:
It is the distinction between indirect and direct taxes depending on the individuals who bear them, as the tax is considered direct when it is borne by the last taxpayer, while the tax is classified as indirect if it is transferred from the taxpayer to another person.

*Income taxes:
They are taxes imposed by states on individuals who live in their communities, and they are considered important taxes. Therefore, many different concepts and definitions have emerged for them among thinkers and writers. These taxes include two types:
- General income tax: It is the dependence of all individual income on one tax only, regardless of the individual's multiple sources of income.
- Income branch tax, also known as specific tax; That is, the tax is imposed according to the type of income of the individual, and this depends on the division of the main sources of income; Where there is income resulting from work and follows the wage tax, and there is income resulting from capital, and follows the tax on movable funds.

The application of taxes depends on a set of basic rules that are considered bases by which states are bound. These rules seek to enhance compatibility between the interests of financiers and the public treasury. The following is information about the most important of these rules:
- The rule of equality: is to consider tax justice as one of the important principles of the effective tax system, as the tax legislature seeks to apply this justice during the distribution of burdens among tax owners, as this concept has developed with the development of societies, so justice for traditionalists is meant as the contribution of all members of society to bear the expenses of the state, according to the relative cost of each of them, i.e., that their contribution is commensurate with their income.

- The certainty rule: a rule that refers to a good tax that is clearly defined; In the sense that it is an explicit and specific tax, the method and date of its collection are known, and its price is clear and specific, and this rule indicates the existence of prior knowledge of the individual charged with the tax from the state.
- The rule of stability: is that tax revenue does not change as a result of economic changes, specifically in the period of economic depression, but tax revenue often increases when production and public incomes increase.
- - The rule of flexibility: is that the change in income is accompanied by a change in the income of taxes in terms of space and time, that is, that flexible taxes are the ones that witness an increase in their value; Because of its high rates, with no shrinkage in its tax base, and consequently a decline in its proceeds.