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.
National Savings and Investments
National Savings and Investments (NS&I), formerly called the Post Office Savings Bank and National Savings, is a state-owned savings bank in the United Kingdom. It is both a non-ministerial government department and an executive agency of the Chancellor of the Exchequer. Historically, the aim of NS&I has been to attract funds from individual savers in the UK for the purpose of funding the government’s public sector borrowing requirement (i.e., the funds in excess of taxation that the government requires to fund its expenditure). NS&I attracts savers through offering savings products with tax-free elements on some products, and a 100% guarantee from HM Treasury on all deposits.