Glossary · Cross-Border
Totalization Agreement
The US–UK Totalization Agreement prevents you paying social security taxes to both countries on the same earnings. It assigns your social security liability to one country, generally based on where you work, evidenced by a certificate of coverage.
In more detail
Without coordination, a cross-border worker could owe US Social Security/Medicare and UK National Insurance on the same income. The Totalization Agreement assigns coverage to one system — generally the country where you physically work, with exceptions for detached/posted workers — and a certificate of coverage proves which applies. For the self-employed, liability usually follows the country of residence, so a US citizen self-employed in the UK typically pays UK National Insurance, not US self-employment tax.
Related terms
Does Totalization Agreement apply to your situation?
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