Under the agreement, a detached worker remains subject only to the social security
            taxation and coverage laws of the country from which the employer transfers the employee
            from or the country the worker transfers their self-employment from provided that
            the worker meet all the
               following conditions:
         
         
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                     The employer or worker expects the period of work in the host country to last no more than five years. The five-year period begins with the date the work in the host country
                        begins or July 1, 1984 (the effective date of the agreement), whichever is later.
                     
                     
                   
                
             
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                     The employment relationship (in the case of employment) or the business activity (in
                        the case of self-employment) existed before the employee transfers from the home country; and
                     
                     
                   
                
             
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                     If an American employer sends an employee to become an employee of the company’s affiliate
                        in Belgium, the American employer must have entered into an agreement with the Internal
                        Revenue Service (IRS) under section 3121(l) of the IRS Code. The 3121(l) provides
                        social security [recommend using lower case] coverage for U.S. citizens and residents
                        employed by the affiliate. In such cases, the employer must still obtain a certificate
                        of coverage to establish the exemption from Belgian social security taxes.
                     
                     
                   
                
             
         
         NOTE: The detached worker rule may apply even if the worker does not go directly from one
            country to the other but first works in a third country.