UK national insurance applies to a variety of different sorts of income. The history and introduction of the NIC system is covered in Simon’s Taxes E8.101. NIC is split into different classes depending on the type of income. See the Overview of NIC Classes, rates and thresholds guidance note for more on the different classes and rates.

This guidance note concentrates on NIC relating to employment income in the UK. As with tax, it is important to understand whether an individual is an employee or self-employed for NIC purposes. See the Categorisation of earners for NIC purposes guidance note and Simon’s Taxes E8.201.

For NIC and self-employment, see the Class 4 national insurance contributions guidance note. For international aspects of NIC, see the Global mobility key principles ― overview guidance note.