Understanding NI on Your Payslip

Key facts

Your NI category letter (usually A) is shown on every payslip.
NI is calculated on your NI-able earnings, which may differ from your gross pay.
NI is separate from Income Tax — different rates, different thresholds, different calculation method.
Your employer also pays NI on your earnings, but this is not shown on your payslip.

Reading NI on Your Payslip

Every payslip in the UK must show your National Insurance contributions. Understanding what the numbers mean helps you check that you are paying the right amount and that your NI record is being built correctly.^[2]

What to Look for on Your Payslip

Your payslip should show the following NI-related information:^[2]

Item	What It Means
NI Category	Your NI category letter (usually A). This determines the rates applied
NI Number	Your unique National Insurance number (e.g. QQ 12 34 56 A)
NI-able Gross	Your earnings subject to NI (may differ from total gross pay)
NI (Employee)	The amount of NI deducted from your pay this period
NI (Employer)	Some payslips show this; many do not. This is your employer’s NI cost
NI YTD	Your total NI contributions paid so far this tax year

Example Monthly Payslip Calculation

For a monthly-paid employee earning £3,000 gross per month (category A):^[1]

Monthly NI calculation (£3,000/month):

Primary Threshold (monthly): £1,048
NI-able earnings: £3,000 − £1,048 = £1,952
All within the UEL (£4,189/month), so rate is 8%
Employee NI: £1,952 × 8% = £156.16

NI-able Pay vs Gross Pay

Your NI-able pay may be lower than your gross pay. Common items that reduce NI-able earnings include:

Salary sacrifice pension contributions — these reduce your gross pay before NI is calculated, saving you NI
Salary sacrifice childcare vouchers (for those on legacy schemes)
Cycle to work scheme payments
Other salary sacrifice benefits

Tip: Salary sacrifice is one of the few ways to reduce your NI bill. If your employer offers pension contributions through salary sacrifice rather than a net-pay arrangement, you save NI as well as Income Tax on the sacrificed amount.

NI vs Tax on Your Payslip

Many employees are confused by why their NI deduction is different from their Income Tax deduction. The key differences are:^[3]

Feature	Income Tax	National Insurance
Calculation	Cumulative (year to date)	Per pay period only
Tax code	Uses your personal tax code (e.g. 1257L)	Uses NI category letter only
Free amount	£12,570 Personal Allowance (spread across the year)	PT per period (e.g. £1,048/month)
Benefits etc.	Tax code may include adjustments for benefits, underpayments, etc.	No adjustments — fixed thresholds
Overtime/bonus	Spread cumulatively — may result in refund later	Charged in full in that period — no smoothing

Checking Your NI Is Correct

To verify your NI deduction is correct for a monthly payslip (category A):

Take your gross pay (or NI-able pay if different)
Subtract the monthly Primary Threshold (£1,048)
If the result is £3,141 or less (i.e. total earnings below the monthly UEL of £4,189), multiply by 8%
If your earnings exceed £4,189/month, the first £3,141 (from £1,048 to £4,189) is at 8%, and the excess is at 2%

Note: Minor rounding differences (a few pence) are normal. NI is calculated using exact weekly or monthly thresholds which can lead to small rounding variations compared to annual figures divided by 12.

Employer NI — The Hidden Cost

Your employer pays secondary Class 1 NI on your earnings at 15% (from April 2025) above the Secondary Threshold of £5,000/year (£417/month). This is not deducted from your pay — it is an additional cost borne by the employer.

For an employee earning £36,000/year, the employer’s NI is approximately £4,650 per year. This means the total cost of employing someone is significantly more than their salary alone.

Your P60 and NI

At the end of the tax year, your employer gives you a P60 showing your total earnings and NI paid for the year. This is useful for:

Checking your annual NI total is correct
Tax return purposes (if you need to file Self Assessment)
Mortgage applications and proof of income
Verifying that your NI record has been updated correctly

Frequently Asked Questions

Why is my NI deduction different from my tax deduction?

NI and Income Tax use completely different rates, thresholds, and calculation methods. Income Tax is calculated cumulatively across the year and uses your personal tax code. NI is calculated per pay period using fixed thresholds and is not affected by your tax code.

What does NI category letter A mean?

Category A is the standard NI category for employees aged 21 to State Pension age. It means you pay 8% on earnings between the Primary Threshold and Upper Earnings Limit, and 2% above. Most employees will see category A on their payslip.

Why is my NI-able pay different from my gross pay?

Certain items are excluded from NI-able earnings, including pension contributions made through salary sacrifice, childcare vouchers (where still in use), and some other salary sacrifice arrangements. These reduce your NI-able pay below your headline gross salary.

Does my employer pay NI on my earnings too?

Yes. Your employer pays secondary Class 1 NI at 15% (from April 2025) on your earnings above the Secondary Threshold (£5,000/year). This is a cost to the employer and is not deducted from your pay. It does not appear on your payslip.

Sources

National Insurance rates and categories — GOV.UK
Understanding your payslip — GOV.UK
National Insurance: introduction — GOV.UK