The United States Tax Court is a court established by Congress under the Constitution. When the Internal Revenue Service has determined a tax deficiency and has sent the notorious 90-day letter, the so-called Notice of Deficiency, you may dispute the deficiency in the Tax Court before paying any disputed amount.
The Tax Court’s jurisdiction also includes the authority to order abatement of interest, award administrative and litigation costs, review certain collection actions, determine relief from joint and several liability on a joint return, redetermine worker classification, adjust partnership items, redetermine transferee liability, make certain types of declaratory judgments, and review awards to whistleblowers who provide information to the Commissioner of Internal Revenue.
The U.S. president appoints all 19 Tax Court judges. Trials are conducted and other work of the Court is performed by those judges. All of the judges have expertise in the tax laws and apply that expertise in a manner to ensure that you are assessed only what they owe, and no more. The main Court is in Washington, D.C., while the judges travel all over the country to conduct trials in various designated cities such as Los Angeles, San Francisco, San Diego and Fresno (where only small tax cases are heard).