What type of tax system is exemplified by an individual whose income increased but their tax payment remained the same?

A regressive tax rate system is characterized by a situation in which individuals with lower incomes pay a higher percentage of their income in taxes compared to those with higher incomes. In this type of system, as a person's income increases, their tax payment does not increase proportionally, which can lead to higher-income individuals experiencing a lower effective tax rate.

The scenario described illustrates that as an individual's income increased, their tax payment remained constant, indicating that the burden of taxation does not escalate with higher earnings. This is typical of a regressive tax system, where increases in income do not translate into equivalent increases in tax liability, causing individuals with lower incomes to pay a proportionately larger share compared to wealthier individuals.

In contrast, a progressive tax system raises the tax rate as income increases, which means higher earners pay a larger percentage of their income in taxes. A flat tax rate system imposes the same tax rate on all income levels, meaning every individual pays the same proportion regardless of their income. A proportional tax rate, similar to the flat tax, also applies the same percentage to everyone, resulting in the same tax burden in relation to income. None of these systems explain the situation where an individual's tax payment does not increase despite higher income.