National Insurance (NI) is a tax system in the United Kingdom paid by workers and employers for funding state benefits. Initially, it was a contributory form of insurance against illness and unemployment, and eventually provided retirement pensions and other benefits. Citizens pay National Insurance contributions to become eligible for State Pension and other benefits. Anyone 16 years old and above is mandated to pay National Insurance provided the employee earns more than £166 a week or the individual is self-employed and makes a profit of £6,205 or more annually. It is necessary to obtain a National Insurance number before starting to pay contributions.