26 U.S. Code § 7444 - Organization
The Tax Court shall at least biennially designate a judge to act as chief judge.
The chief judge may from time to time divide the Tax Court into divisions of one or more judges, assign the judges of the Tax Court thereto, and in case of a division of more than one judge, designate the chief thereof. If a division, as a result of a vacancy or the absence or inability of a judge assigned thereto to serve thereon, is composed of less than the number of judges designated for the division, the chief judge may assign other judges to the division or direct the division to proceed with the transaction of business without awaiting any additional assignment of judges thereto.
A majority of the judges of the Tax Court or of any division thereof shall constitute a quorum for the transaction of the business of the Tax Court or of the division, respectively. A vacancy in the Tax Court or in any division thereof shall not impair the powers nor affect the duties of the Tax Court or division nor of the remaining judges of the Tax Court or division, respectively.