Also known as International Social Security agreements, the United States has 25 "totalization agreements" currently in place. The first one is with Italy and dates back to November 1, 1978, and the most recent was agreed upon with the Slovak Republic on May 1, 2014.

Per the U.S social security website, "Without some means of coordinating Social Security coverage, people who work outside their country of origin may find themselves covered under the systems of two countries simultaneously for the same work. When this happens, both countries generally require the employer and employee or self-employed person to pay Social Security taxes."

These totalization agreements eliminate dual Social Security taxation, the situation that occurs when a worker from one country works in another country and is required to pay Social Security taxes to both countries on the same earnings. Second, the agreements help fill gaps in benefit protection for workers who have divided their careers between the U.S. and another country.

Check out this video, where Mike Phillips tells you more!