2. Category letters

Employers use an employee’s National Insurance category letter when they run payroll to work out how much they both need to contribute.

Most employees have category letter A. Employees can find their category letter on their payslip.

Category letter Employee group
A All employees apart from those in groups B, C, J, H, M and Z in this table
B Married women and widows entitled to pay reduced National Insurance
C Employees over the State Pension age
J Employees who can defer National Insurance because they’re already paying it in another job
H Apprentice under 25
M Employees under 21
Z Employees under 21 who can defer National Insurance because they’re already paying it in another job

Employees in a contracted-out money purchase scheme

This kind of scheme ended in April 2012 but some employees might still be part of one.

Category letter Employee group
F Tax years before 2012 to 2013 only: all employees apart from the ones in groups G, C and S in this table
G Tax years before 2012 to 2013 only: married women and widows entitled to pay reduced National Insurance
C Employees over the State Pension age
S Tax years before 2012 to 2013 only: employees who can defer National Insurance because they’re already paying it in another job

Category letter X

Employers use category letter X for employees who don’t have to pay National Insurance, eg because they’re under 16.

Mariners and deep sea fishermen

HMRC has detailed information on National Insurance for mariners and deep sea fishermen.