Federal tax law refers to every statute, regulation, court decision, and other legal authority relating to the imposition of any tax by the federal government of the United States.
Other authorities include decisions and advice issued by the Internal Revenue Service, which generally take one of the following forms: revenue ruling, revenue procedure, private letter ruling, technical advice memorandum, field service advice memorandum, general counsel memorandum, or chief counsel advice.
[Last updated in January of 2023 by the Wex Definitions Team]