Employers NI Calculator (UK)
Estimate standard Class 1 secondary National Insurance for an employee. Enter gross pay, choose a pay frequency, and adjust thresholds/rates if needed for your payroll setup.
Estimator only. Payroll outcomes can differ by NI category letter, age-based reliefs, apprenticeship status, and HMRC rule changes.
If you are searching for a practical employers NI calculator, this page gives you a quick way to model payroll costs without opening a spreadsheet. It focuses on standard employer National Insurance, also known as Class 1 secondary contributions, which is one of the biggest on-costs after gross salary.
What is employers NI?
Employers NI is a UK payroll tax paid by the employer on qualifying employee earnings above a threshold. In simple terms, once pay goes over the relevant secondary threshold, you apply the employer NI rate to the amount above that threshold.
- Who pays it: The employer (not deducted from employee net pay as employer NI).
- When it applies: On earnings above the employer threshold.
- Why it matters: It affects total cost of hiring, budgeting, and cash flow planning.
How this calculator works
The calculator annualises pay first, then applies the NI settings you select. You can either use a tax-year preset or overwrite the threshold and rate manually.
Formula used
Annual Employer NI (before allowance) = max(0, Annual Gross Pay − Annual Secondary Threshold) × Employer NI Rate
Annual Employer NI (after allowance) = max(0, NI Before Allowance − Employment Allowance Used)
Per-period NI = Annual Employer NI ÷ Pay periods per year
Pay period multipliers
- Annual: 1
- Monthly: 12
- Weekly: 52
- Four-weekly: 13
- Daily: 260 working days
Worked example
Suppose gross pay is £3,000 monthly. Annualised pay is £36,000. If your selected threshold is £5,000 and the rate is 15%, NI is calculated on £31,000:
- Taxable earnings for employer NI: £36,000 − £5,000 = £31,000
- Employer NI before allowance: £31,000 × 15% = £4,650
- If no allowance remains, annual NI due = £4,650
- Monthly equivalent = £4,650 ÷ 12 = £387.50
What can change your result
1) NI category and reliefs
This calculator is intentionally simple and targets standard scenarios. In real payroll, NI category letters and special reliefs (for example age or apprentice-related rules) can materially change liability.
2) Employment Allowance
If your business qualifies, Employment Allowance can reduce the total employer NI bill. Use the allowance input to estimate how much of your annual contribution may be offset.
3) Mid-year rule updates
Thresholds and rates can change with new budgets or tax policy updates. The preset values are useful for quick estimates, but always confirm with current HMRC guidance before filing payroll.
Why employers use an NI calculator
- Compare true cost of part-time vs full-time hires.
- Forecast annual payroll taxes for budgeting.
- Estimate impact of salary increases or bonuses.
- Support pricing decisions for service businesses with tight margins.
Common mistakes to avoid
- Using employee NI assumptions instead of employer NI settings.
- Mixing monthly pay data with annual thresholds incorrectly.
- Forgetting to account for remaining Employment Allowance.
- Assuming rates are static year after year.
Final note
An employers NI calculator is best used as a planning tool. For payroll submissions, compliance, and year-end reconciliation, always verify settings in your payroll software and check official HMRC documentation for the applicable tax year.