Yes. Congress established the United States Tax Courts under Article I of the Constitution to handle disputes with the Internal Revenue Service.
While the US Tax Court is part of the federal judicial system, it is independent of the Article III Courts, like the US Supreme Court and other courts of general jurisdiction, and is not considered part of the Judicial Branch of government.
Confusing? The judicial system includes all courts; the Judicial Branch is one of the three controlling parts of the US government, and includes only those courts established under Article III to deal specifically with federal and constitutional law and treaties.
For more information, see Related Questions, below.