A treaty between the US and another country that decides which country's social security system a worker pays into, so the same wages are not taxed for social security by both.
Without an agreement, a self-employed expat can owe US self-employment tax and the local country's contributions on the same income. With one, a certificate of coverage from the country you pay into exempts you from the other. The US has agreements with about 30 countries.
No. Only a totalization agreement, or paying into the other country's system under one, removes US self-employment tax for an expat.
Source: Social Security Administration international agreements
Last reviewed September 17, 2026. Tax rules change; confirm current law before acting.
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