20 CFR § 404.1913 - Precluding dual coverage.
(a)General. Employment or self-employment or services recognized as equivalent under the Act or the social security system of the foreign country shall, on or after the effective date of the agreement, result in a period of coverage under the U.S. system or under the foreign system, but not under both. Methods shall be set forth in the agreement for determining under which system the employment, self-employment, or other service shall result in a period of coverage.
(b)Principles for precluding dual coverage.
(1) An agreement precludes dual coverage by assigning responsibility for coverage to the U.S. or a foreign country. An agreement may modify the coverage provisions of title II of the Act to accomplish this purpose. Where an agreement assigns coverage to the foreign country, it may exempt from coverage services otherwise covered by the Act. Where an agreement assigns coverage to the U.S., it may extend coverage to services not otherwise covered by the Act but only for taxable years beginning on or after April 20, 1983.
(2) If the work would otherwise be covered by both countries, an agreement will exempt it from coverage by one of the countries.
(3) Generally, an agreement will provide that a worker will be covered by the country in which he or she is employed and will be exempt from coverage by the other country.
(5) Generally, if a national of either country resides in one country and has self employment income that is covered by both countries, an agreement will provide that the person will be covered by the country in which he or she resides and will be exempt from coverage by the other country.
(6)Agreements may provide for variations from the general principles for precluding dual coverage to avoid inequitable or anomalous coverage situations for certain workers. However, in all cases coverage must be provided by one of the countries.