n [ U ] (abbr NI )
( in Britain ) a system of payments, called National Insurance contributions , that all working people and employers have to make. The money is used by the government for payments to unemployed people and others in need, and also to help pay for the National Health Service . National Insurance is therefore an important part of the welfare state . Every adult has a National Insurance number and this number is used by the Department for Work and Pensions to identify people.