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.
Information Technology Services Agency
Information Technology Services Agency (ITSA) was an executive agency of the United Kingdom Department of Social Security (subsequently the Department for Work and Pensions) which was set up in 1991 to "help create and deliver an active modern social security service, which encourages and enables independence and aims to pay the right money at the right time". ITSA ceased to exist in 2000, following the outsourcing of the majority of its functions and staff to Electronic Data Systems (EDS).