Federal tax is a domain of inquiry within public finance, law, economics, and political science concerned with the principles, structures, administration, and effects of taxes levied by a central or federal governmental authority. As a research concept, it investigates the legislative frameworks, institutional mechanisms, economic impacts, social implications, and historical or political dynamics shaping federal taxation policy and practice, serving as a critical concept for understanding government finance, economic behavior, income distribution, and the relationship between the state and its citizens.