A progressive tax system is designed so that the average tax rate increases as the taxpayer's income increases. This structure is intended to reduce the tax burden on lower-income individuals while placing a higher relative burden on those with greater financial capacity, thereby promoting vertical equity within the tax system.

Horizontal equity is a fundamental principle of fair taxation which posits that individuals who possess the same economic capacity or ability to pay should be treated identically by the tax system. This means that taxpayers in similar financial circumstances should face the same tax liability, thereby preventing arbitrary discrimination between individuals with comparable income levels or wealth.

A proportional tax, often referred to as a flat tax, applies a constant tax rate to all taxpayers regardless of their income level. Because the rate remains fixed, the percentage of income paid as tax is identical for every household, ensuring that the tax burden scales linearly with income rather than increasing or decreasing as a share of total earnings.

The marginal tax rate is the rate of tax applied to the last unit of currency earned. It represents the change in total tax liability resulting from a small change in taxable income. This is distinct from the average tax rate, which is the total tax paid divided by total income, and is essential for understanding the incentive effects of taxation on labor and investment.

The marginal tax rate is defined as the rate of tax applied to the last unit of currency earned. Mathematically, it is calculated as the ratio of the change in total tax paid to the change in total income. This metric is essential for understanding how additional earnings are taxed and how tax systems influence incentives for individuals to work more or earn higher income.

Progressive taxation is a system where the tax rate increases as the taxable amount increases. By taxing higher earners at a larger percentage, the government can redistribute wealth through public services and social welfare programs, thereby reducing income inequality and narrowing the gap between the rich and the poor in the society.

While taxes are often used to correct negative externalities, in the context of merit goods, governments may impose taxes or regulations to influence consumption patterns. Note: This answer is controversial as taxes are typically used to discourage demerit goods rather than merit goods, which are often subsidized.

Bracket creep occurs in progressive tax systems when nominal income increases due to inflation, pushing individuals into higher tax brackets. Even if their real purchasing power has not increased, they pay a higher percentage of their income in taxes. This effectively increases the government's tax revenue without an explicit legislative change to tax rates, which can act as a drag on economic growth.

In many fiscal systems, the General Sales Tax (GST) is a major source of federal revenue. While tax jurisdictions vary by country, GST is frequently managed at the national level to ensure uniformity across states or provinces, whereas property taxes are often managed by local or provincial governments.

Sales tax is an indirect tax imposed by the government on the sale of goods and services. It is collected by the retailer at the point of sale from the consumer and subsequently remitted to the government authorities, acting as a consumption-based revenue source.