The term Secretary or his delegate means the Secretary of the Treasury, or any officer, employee, or agency of the Treasury Department duly authorized by the Secretary (directly, or indirectly by one or more redelegations of authority) to perform the function mentioned or described in the context, and the term “or his delegate” when used in connection with any other official of the United States shall be similarly construed.

In any case in which a function is vested by the Internal Revenue Code of 1954 or any other statute in the Secretary or his delegate, and Treasury regulations or Treasury decisions approved by the Secretary or his delegate provide that such function may be performed by the Commissioner, assistant commissioner, regional commissioner, assistant regional commissioner, district director, director of a regional service center, or by a designated officer or employee in the office of any such officer, such provision in the regulations or Treasury decision shall constitute a delegation by the Secretary of the authority to perform such function to the designated officer or employee. If such authority is delegated to any officer or employee performing services under the supervision and control of the Commissioner, such provision in the regulations or Treasury decision shall constitute a delegation by the Secretary to the Commissioner of the authority to perform such function and a redelegation thereof by the Commissioner to the designated officer or employee.

An officer or employee, including the Commissioner, authorized by regulations or Treasury decision to perform a function shall have authority to redelegate the performance of such function to any officer or employee performing services under his supervision and control, unless such power to so redelegate is prohibited or restricted by proper order or directive. The Commissioner may also redelegate authority to perform such function to other officers or employees under his supervision and control and, to the extent he deems proper, may authorize further redelegation of such authority.

The Commissioner may prescribe such limitations as he deems proper on the extent to which any officer or employee under his supervision and control shall perform any such function, but, in the case of an officer or employee designated in regulations or Treasury decision as authorized to perform such function, such limitations shall not render invalid any performance by such officer or employee of the function which, except for such limitations, such officer or employee is authorized to perform by such regulations or Treasury decision in effect at the time the function is performed.