"Totalization Agreements" are a common term for a network of Social Security bilateral agreements with other countries that have programs comparable to Social Security. They have been designed over the years to account for two main issues:
- Dual taxation - The situation that occurs when a worker from one country working in another country is essentially required to pay Social Security taxes to both countries on the same earnings.
- Gaps in Benefit Protection - The agreements help fill the gaps in benefit protection for workers who have divided their careers between the U.S. and another country.
More detail is available at https://www.ssa.gov/international/agreements_overview.html