Tax law or revenue law is an area of legal study in which public or sanctioned authorities, such as federal, state and municipal governments (as in the case of the US) use a body of rules and procedures (laws) to assess and collect taxes in a legal context. The rates and merits of the various taxes, imposed by the authorities, are attained via the political process inherent in these bodies of power, and not directly attributable to the actual domain of tax law itself.

Tax law is part of public law. It covers the application of existing tax laws on individuals, entities and corporations, in areas where tax revenue is derived or levied, e.g. income tax, estate tax, business tax, employment/payroll tax, property tax, gift tax and exports/imports tax. There have been some arguments that consumer law is a better way to engage in large-scale redistribution than tax law because it does not necessitate legislation and can be more efficient, given the complexities of tax law.^: 213