Part II is intended to eliminate dual coverage, i.e., situations where a worker is covered under the laws of both countries with respect to the same services. In so doing, the existing coverage provisions of the laws of both countries are preserved to the greatest extent possible. The provisions in this Part are intended to eliminate dual coverage by continuing the worker's social security coverage and taxation under the system of the country to whose economy he has the more direct connection and exempting him from coverage and taxation under the other country's system.
Article 4 establishes general rules for eliminating dual social security coverage and contributions for employment and self-employment. Article 5.1 contains an exception to these general rules which would apply in the case of employees sent by an employer in one country to work temporarily in the other country. Article 5.2 provides a special rule that applies to work activity that is considered employment by one country and self-employment by the other country. Article 5.3 regulates the coverage of persons engaged in international air or ship transportation. Article 6 establishes rules applicable to persons employed in U.S. or Portuguese Government service.