If both the U.S. and Icelandic social security systems cover a worker’s employment
or self-employment, the agreement provides that beginning March 1, 2019, only one
country’s system covers the worker’s employment or self-employment. The agreement
does not affect a worker’s coverage prior to that date. If a worker had dually covered
earnings before March 1, 2019, those earlier earnings were and would continue to be
subject to social security contributions in both countries.