The U.S. has Social Security totalization agreements with 30 countries that stop you paying into two systems at once — and let you combine credits toward a U.S. benefit. Most sites only explain it. This one calculates it.
Estimate where you owe social security tax abroad and whether you can combine credits for a U.S. benefit.
Every country with a U.S. Social Security totalization agreement in force.
A totalization agreement is a treaty between the U.S. and another country that coordinates Social Security coverage for people who work across borders. It does two things:
1. Eliminates dual coverage. Without an agreement, a worker sent abroad can owe social security taxes to both countries on the same earnings. The agreement assigns you to just one system — usually your home country for assignments under 5 years (the "detached worker" rule), and the host country otherwise.
2. Lets you combine credits. U.S. retirement benefits normally require 40 quarters (10 years) of credits. If you have at least 6 quarters of U.S. credits, the agreement lets you "totalize" — combine your U.S. and foreign credits — to qualify for a pro-rated U.S. benefit you'd otherwise lose.