Glossary · UK Tax
National Insurance
National Insurance is the UK social security contribution system, funding the state pension and certain benefits. For cross-border workers, the US–UK Totalization Agreement decides whether NI or US Social Security applies.
NI
In more detail
NI is paid by employees, employers, and the self-employed to build entitlement to the UK state pension and some benefits. For someone working across both countries, the Totalization Agreement prevents double social-security charges by assigning liability to one system. A US citizen self-employed in the UK generally pays UK NI rather than US self-employment tax, evidenced by a certificate of coverage. (Class 2 self-employed NI was abolished from April 2024.)
Related terms
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