National Insurance Calculator: Step-by-Step for 2026-27

The employer rate of National Insurance is 15% on earnings above £5,000 per year, and the employee rate is 8% on earnings between £12,570 and £50,270, making accurate NI calculation a higher-stakes obligation than in any previous tax year ^[1][2]. For an employee earning £30,000 per year, those two rates produce a combined NI cost to employer and employee of over £5,100 per year.

Every UK employer must calculate the correct NI for each employee every pay period, submit the figures to HMRC via a Full Payment Submission on or before payday, and pay both shares by the 22nd of the following month ^[3]. The method below follows HMRC's preferred exact percentage approach for Class 1 National Insurance, which is the method required for payroll software that holds the HMRC Recognised badge.

Key takeaways

• Employee NI is 8% on earnings between £12,570 and £50,270 per year, and 2% above that figure.
• Employer NI is 15% on all earnings above £5,000 per year, with no upper limit.
• The calculation uses the period threshold (weekly or monthly), not an annual figure divided down pro rata.
• Earnings between the Lower Earnings Limit (£6,708) and the Primary Threshold (£12,570) must be recorded even though no NI deduction applies.
• A £30,000 annual salary produces employee NI of approximately £1,394 and employer NI of approximately £3,750 per year.

The thresholds you need

Before calculating, identify the thresholds relevant to the pay frequency. HMRC publishes weekly, monthly and annual versions, and the period version must be used, not the annual figure divided by the number of periods ^[1][2].

The UST, which determines where the zero-employer-NI relief ends for under-21s and apprentices under 25, equals the UEL for the 2026-27 tax year ^[1].

Calculating employee NI step by step

For a standard Category A employee paid monthly ^[4][1]:

1. Take the employee's gross NIable pay for the period.
2. If gross pay is below the LEL (£559 per month): no NI due and no qualifying-year record applies.
3. If gross pay is between the LEL and the PT (£559 to £1,048 per month): record the earnings but deduct no employee NI. The employee gains a qualifying year for State Pension purposes.
4. If gross pay is above the PT: subtract £1,048 from the gross pay to find the amount subject to employee NI.
5. On the earnings from the PT to the UEL (£1,048 to £4,189 per month): apply 8%.
6. On earnings above the UEL (above £4,189 per month): apply 2%.
7. Add the two results and round to the nearest penny. HMRC specifies rounding to the nearest penny: where the third decimal place is 5 or below, round down; where it is 6 or above, round up ^[1].

Calculating employer NI step by step

For a standard employer with a Category A, B or C employee ^[4][2]:

1. Take the employee's gross NIable pay for the period.
2. If gross pay is below the ST (£417 per month): no employer NI due.
3. If gross pay is above the ST: subtract £417 from the gross pay.
4. Apply 15% to all earnings above the ST. There is no upper limit for employer NI.
5. Round to the nearest penny.

For employers with Category M or H employees (under-21 or apprentice under 25), apply 0% on earnings up to the UST (£4,189 per month) and 15% on any earnings above that ^[1].

Worked example: £30,000 annual salary, Category A, paid monthly

Monthly gross pay: £2,500.

Employee NI:

Monthly PT: £1,048. Earnings above PT: £2,500 minus £1,048 equals £1,452. Employee NI: £1,452 multiplied by 8% equals £116.16 per month ^[4]. Annual employee NI: £116.16 multiplied by 12 equals £1,393.92.

Employer NI:

Monthly ST: £417. Earnings above ST: £2,500 minus £417 equals £2,083. Employer NI: £2,083 multiplied by 15% equals £312.45 per month ^[2]. Annual employer NI: £312.45 multiplied by 12 equals £3,749.40.

Total combined NI cost per year for this employee: £5,143.32.

HMRC-recognised payroll software performs this calculation automatically for every employee on every payrun, but understanding the underlying method is essential for checking outputs and handling special cases.

Special cases that change the calculation

Earnings above the Upper Earnings Limit

For employees whose pay exceeds £4,189 per month, the employee rate drops from 8% to 2% on the excess above the UEL ^[1]. The employer continues at 15% on all earnings above the ST, with no ceiling. For a director-shareholder earning £80,000 per year, the employer NI is 15% on £75,000 (the £80,000 minus the £5,000 ST), equal to £11,250 per year ^[2].

Category M and H: zero employer NI up to the UST

Where the employee is under 21 (category M) or an apprentice under 25 on a registered programme (category H), the employer NI rate on earnings up to £50,270 per year is 0% ^[1][3]. Applying the worked example above to a Category M employee: employer NI would be £0 rather than £3,749.40. The correct category letter must be confirmed before the first payrun, because the system will otherwise default to Category A and overcharge the employer for every period until the error is corrected.

Directors: annual earnings period

Directors are not assessed on a period-by-period basis. Instead, HMRC applies the annual thresholds against the director's cumulative earnings for the tax year ^[3][4]. A director who takes a low salary each month and a larger payment later in the year will see the NI recalculated on the running total when the larger payment is processed, often producing a concentrated NI charge in that period. Payroll systems that do not implement the annual method for directors will generate wrong NI figures every period.

For accountants managing bureau payrolls, directors are the single most frequent source of NI calculation errors in client payrolls, because the annual earnings period requirement is not obvious and is not applied by default in all payroll products. The understanding employer national insurance article on the Moonworkers blog covers the annual earnings period in full.

Category B: the reduced rate for married women

A small number of employees hold a valid reduced-rate election made before 1977, known as the married woman's reduced rate. These employees pay primary NI at 1.85% on earnings between the Primary Threshold and the Upper Earnings Limit, and 2% above the UEL, rather than the standard 8% ^[1]. The employer's rate remains at 15% regardless. No new elections can be made today; the reduced rate applies only to existing valid holders. In a worked example with a monthly salary of £2,500, a Category B employee's NI would be £1,048 × 1.85% = £19.39 rather than the Category A result of £116.16.

Freeport and Investment Zone employees (categories F, I, S, L)

Employees working in a designated Freeport or Investment Zone tax site attract a 0% employer NI rate on earnings up to a Freeport Upper Secondary Threshold (FUST) of £25,000 per year (£2,083 per month, £481 per week) ^[1]. The standard 15% applies on any earnings above that threshold. In the worked example at £2,500 per month, a Freeport-eligible employer would pay 0% on the first £2,083 and 15% on £417 (£2,500 minus £2,083), equal to £62.55 per month rather than £312.45. The relief requires the employee to spend at least 60% of working time at the designated site and applies for up to 36 months per eligible employee.

How payroll software handles this

The NI calculation above has six variables per employee: the pay frequency, the NI category letter, the gross NIable pay, the applicable thresholds for that frequency, the relevant rates, and whether the director method applies. For a ten-person payroll with mixed categories, that is sixty data points to maintain and recalculate every period. A small business payroll platform handles all of them automatically, including the April threshold refresh. Software that automates the calculation also handles threshold updates each April automatically, so employers do not need to manually update figures when the tax year changes.

The Moonworkers payroll API implements HMRC's exact percentage method for all NI category letters, including Freeport and Investment Zone categories, handles the directors' annual earnings period, and returns the primary and secondary NI figures as separate fields in the API response for every employee.

Calculate National Insurance instantly

The Moonworkers National Insurance calculator applies the 2026-27 thresholds and the 8% and 2% employee bands, alongside the 15% employer rate, to any salary or hourly rate. It also reflects the reduced employer rates for categories M, H and V.

Conclusion

The NI calculation is mechanical once the thresholds and category letter are known, but those two inputs are where errors concentrate. An employer who runs employees on the wrong category overpays or underpays employer NI for every period until the mistake is found. One whose software uses the monthly method for directors generates wrong deductions throughout the year.

For sole traders and director-only companies, the calculation is straightforward at low earnings but becomes complex when a salary-plus-dividend structure pushes cumulative director earnings past the Primary Threshold late in the tax year. In both cases, software that implements the correct method reliably is worth more than a manual spreadsheet that implements it approximately.

Frequently asked questions

How do I calculate employer National Insurance on a monthly salary?

Subtract the monthly Secondary Threshold (£417) from the employee's gross monthly pay, then multiply the result by 15% ^[2]. For a monthly salary of £2,500: £2,500 minus £417 equals £2,083; £2,083 multiplied by 15% equals £312.45. That amount is payable to HMRC as part of the monthly PAYE bill, in addition to the employee's own NI deduction and income tax.

What is the employee NI rate for the 2026-27 tax year?

Employees pay 8% on earnings between the Primary Threshold (£1,048 per month) and the Upper Earnings Limit (£4,189 per month), and 2% on any earnings above the Upper Earnings Limit ^[1]. No employee NI is due on earnings below £1,048 per month. Earnings between the Lower Earnings Limit (£559 per month) and the Primary Threshold must still be recorded by the employer, because they count towards qualifying years for the State Pension.

Does an employer pay NI on an employee under 21?

No. Employers pay 0% NI on earnings up to £50,270 per year (£4,189 per month) for employees under 21, who are assigned category M ^[1]. The standard 15% rate applies on any earnings above £50,270. The employee still pays their own NI at the standard rates. The correct category letter must be set in the payroll system before the first payrun: the system will default to Category A if it is not set, and the employer will be overcharged on every payrun until the error is corrected.

How does the NI calculation differ for company directors?

Directors are assessed on an annual earnings period rather than a weekly or monthly one, meaning NI is calculated on their total cumulative earnings for the tax year rather than on each individual payment ^[3]. The annual Primary Threshold (£12,570) and Upper Earnings Limit (£50,270) are applied against the running total. A director who takes a minimal salary for most of the year and a larger sum near year-end will see NI concentrated in the later pay periods rather than spread evenly, which is the correct treatment under HMRC rules.