UK PAYROLL
National Insurance, explained.
Understand what your NI category means, how the rates apply to your pay, and why the deduction can change between months even when your salary is the same.
Educational estimates only. Not tax, legal, financial, payroll or employment advice. Verify with your employer's payroll team or HMRC.
Read more on National Insurance
NI Category A
The default category for most UK employees.
NI on overtime
How working an extra hour is treated.
NI on bonus
Why bonuses spike your monthly NI bill.
Why has my NI changed
The most common reasons for a sudden change.
NI vs income tax
Two deductions, two different rate structures.
NI at state pension age
When NI stops being deducted from your pay.
Common questions
What is National Insurance?
National Insurance is a UK payroll deduction that funds state benefits like the State Pension, statutory sick pay, statutory maternity pay and Jobseeker's Allowance. It is calculated weekly or monthly on the portion of your pay above the Primary Threshold, at a rate that depends on your NI category letter.
What is my NI category letter?
Most employees are Category A. Other categories (B, C, H, J, M, X) cover specific groups such as state pensioners, married women paying the reduced rate, and apprentices. Your category is shown on your payslip.
Why has my NI changed this month?
Common causes include earning above the Upper Earnings Limit and shifting into the 2 percent rate, receiving a bonus or overtime, switching jobs partway through the month, a change in NI category, or HMRC adjusting your tax code in a way that changes your taxable pay.
Can I get an NI refund?
In some cases, yes. If you paid NI in two jobs simultaneously and exceeded the annual maximum, or if you were charged at the wrong category, HMRC may issue a refund. Contact HMRC on 0300 200 3500 to query.
Run the NI Calculator
Free. Private. No signup.
Open the toolPayslipIQ provides educational information and estimated calculations only. It does not provide tax, legal, financial, payroll, accounting, pension, benefits or employment advice. Always verify your payslip, tax code, deductions and take-home pay with your employer's payroll department, HMRC, your pension provider, a qualified accountant, tax adviser or another appropriately qualified professional.