The Commissioner of Social Security shall, at the request of any Indian tribe, enter into an agreement with such Indian tribe for the purpose of extending the insurance system established by this subchapter to services performed by individuals as members of such Indian tribe’s tribal council. Any agreement with an Indian tribe under this section applies to all members of the tribal council, and shall include all services performed by individuals in their capacity as council members.

Notwithstanding section 410(a) of this title, for the purposes of this subchapter, the term “employment” includes any service included under an agreement entered into under this section.

The term “member” means, with respect to a tribal council, an individual appointed or elected to serve as a member or the head of the tribal council.

The term “tribal council” means the appointed or elected governing body of a federally recognized Indian tribe.

Any agreement under this section shall be effective with respect to services performed after an effective date specified in such agreement, provided that such date may not be earlier than the first day of the next calendar month after the month in which the agreement is executed by both parties.

At the request of the Indian tribe at the time of the agreement, such agreement may apply with respect to services performed before such effective date for which there were timely paid in good faith (and not subsequently refunded) to the Secretary of the Treasury amounts equivalent to the sum of the taxes which would have been imposed by sections 3101 and 3111 of the Internal Revenue Code of 1986 had such services constituted employment for purposes of chapter 21 of such Code. No agreement under this section may require payment to be made after the effective date specified in such agreement of any taxes with respect to services performed before such effective date.