The function of a tax system is to provide the governments with sources of revenues. Here are some possible tax systems:

A progressive tax means that as incomes increase, the percentage of income paid in taxes also increases. In a progressive tax system, higher income earners pay more dollars in taxes than do lower income earners, and higher income earners also pay a greater percentage of their income in taxes.

A proportional tax system (“flat tax”) means that all income earners pay the same percentage of income in taxes, but higher income earners pay more dollars than do lower income earners. A person earning $100,000 will pay more dollars than will a person earning $10,000. Both, however, will pay the same percentage of income in tax.

A regressive tax system means that higher income earners will pay a smaller percentage of their income in taxes, than will lower income earners, However, it is possible that higher income earners will pay more dollars in tax than will lower income earners, even though the dollars represent a smaller percentage of income for higher income earners. The most common example of a regressive tax is the sales tax.

Negative Income Tax System - MIT - https://mitsloan.mit.edu/ideas-made-to-matter/negative-income-tax-explained#:~:text=What%20is%20negative%20income%20tax,money%20back%20from%20the%20government.

Consumption Tax - https://www.econlib.org/library/Enc/ConsumptionTax.html