In the case of the taxes imposed by this chapter with respect to service performed in the employ of the United States or in the employ of any instrumentality which is wholly owned by the United States, including such service which is medicare qualified government employment (as defined in section 3121(u)(3)), including service, performed as a member of a uniformed service, to which the provisions of section 3121(m)(1) are applicable, and including service, performed as a volunteer or volunteer leader within the meaning of the Peace Corps Act, to which the provisions of section 3121(p) are applicable, the determination of the amount of remuneration for such service, and the return and payment of the taxes imposed by this chapter, shall be made by the head of the Federal agency or instrumentality having the control of such service, or by such agents as such head may designate. In the case of the taxes imposed by this chapter with respect to service performed in the employ of an international organization pursuant to a transfer to which the provisions of section 3121(y) are applicable, the determination of the amount of remuneration for such service, and the return and payment of the taxes imposed by this chapter, shall be made by the head of the Federal agency from which the transfer was made. Nothing in this paragraph shall be construed to affect the Secretary's authority to determine under subsections (a) and (b) of section 3121 whether any such service constitutes employment, the periods of such employment, and whether remuneration paid for any such service constitutes wages. The person making such return may, for convenience of administration, make payments of the tax imposed under section 3111 with respect to such service without regard to the contribution and benefit base limitation in section 3121(a)(1), and he shall not be required to obtain a refund of the tax paid under section 3111 on that part of the remuneration not included in wages by reason of section 3121(a)(1). Payments of the tax imposed under section 3111 with respect to service, performed by an individual as a member of a uniformed service, to which the provisions of section 3121(m)(1) are applicable, shall be made from appropriations available for the pay of members of such uniformed service. The provisions of this section shall be applicable in the case of service performed by a civilian employee, not compensated from funds appropriated by the Congress, in the Army and Air Force Exchange Service, Army and Air Force Motion Picture Service, Navy Exchanges, Marine Corps Exchanges, or other activities, conducted by an instrumentality of the United States subject to the jurisdiction of the Secretary of Defense, at installations of the Department of Defense for the comfort, pleasure, contentment, and mental and physical improvement of personnel of such Department; and for purposes of this section the Secretary of Defense shall be deemed to be the head of such instrumentality. The provisions of this section shall be applicable also in the case of service performed by a civilian employee, not compensated from funds appropriated by the Congress, in the Coast Guard Exchanges or other activities, conducted by an instrumentality of the United States subject to the jurisdiction of the Secretary of the Department in which the Coast Guard is operating, at installations of the Coast Guard for the comfort, pleasure, contentment, and mental and physical improvement of personnel of the Coast Guard; and for purposes of this section the Secretary of the Department in which the Coast Guard is operating shall be deemed to be the head of such instrumentality.