What countries currently use flat tax system?

As of October 2023, several countries employ a flat tax system, where a single tax rate is applied to all income levels. Notable examples include Estonia, Latvia, and Lithuania in Europe, as well as countries like Russia and Hungary. Additionally, some jurisdictions, such as certain states in the United States like Texas and Florida, have no state income tax, which can function similarly to a flat tax approach. These systems aim to simplify tax administration and encourage economic growth.