The agreement with Poland became effective March 1, 2009.

Workers whose employment or self-employment would otherwise be covered by both the U.S. and Polish social security systems are covered and taxed for social security purposes by only one country's system beginning March 1, 2009. The agreement does not affect a worker's taxation or coverage prior to that date. If a worker had earnings before March 1, 2009 that were dually covered, those earnings were subject to social security taxes in both countries.