
National Insurance (NI) is a fundamental component of the welfare state in the United Kingdom. It acts as a form of social security, since payment of NI contributions establishes entitlement to certain state benefits for workers and their families.

The National Insurance Act 1911 created National Insurance, originally a system of health insurance for industrial workers in Great Britain based on contributions from employers, the government, and the workers themselves. It was one of the foundations of the modern welfare state. It also provided unemployment insurance for designated cyclical industries. It formed part of the wider social welfare reforms of the Liberal Governments of 1906–1915, led by Henry Campbell-Bannerman and H. H. Asquith. David Lloyd George, the Liberal Chancellor of the Exchequer, was the prime moving force behind its design, negotiations with doctors and other interest groups, and final passage, assisted by Home Secretary Winston Churchill.

The National Insurance Act 1946 was a British Act of Parliament passed during the Attlee ministry which established a comprehensive system of social security throughout the United Kingdom.

The National Insurance Contributions Act 2006 is an Act of the Parliament of the United Kingdom. It amends the law relating to national insurance contributions. Its precursor was an announcement made in the Paymaster General's Pre-Budget Report 2004.

The National Insurance Contributions Act 2008 is an Act of the Parliament of the United Kingdom which amends the law in relation to National insurance contribution.

The National Insurance Contributions Act 2014 is an Act of the Parliament of the United Kingdom that received Royal Assent on 13 March 2014, after being introduced on 12 October 2013. The act entitled employers to an allowance up to £2,000 against their National Insurance Contributions liability for a tax year.

The National Insurance Contributions and Statutory Payments Act 2004 is an Act of the Parliament of the United Kingdom.

The three British National Insurance Funds hold the contributions of the National Insurance Scheme, set up by the Government of the United Kingdom in 1911. It was reformed in 1948 and assumed broadly its current form in 1975, when the separate National Insurance and National Insurance (Reserve) Funds were merged with it. In the Beveridge Report this was the basis of a universal insurance system for all British people. "first and foremost a plan of insurance – of giving in return for contributions benefits up to subsistence levels, as of right and without means test, so that individuals may build freely upon it".