National Insurance number
The National Insurance number is used as a reference number in the Pay As You Earn system, and also by the self-employed. It is also used in applications for Individual Savings Accounts (ISAs), to check that an individual has opened only one ISA in a tax year.
Social Security Administration Act 1992
The Social Security Administration Act 1992 (c 5) is the main piece of legislation dealing with the administration of social security benefits in the United Kingdom.