Alongside Income Tax, National Insurance (NI) is one of the two biggest deductions on a UK payslip — yet it works on its own separate set of thresholds and rates, which trips up a lot of employees, employers, and self-employed workers alike. Understanding how NI is actually calculated matters whether you're checking your own payslip, budgeting as a sole trader, or working out payroll costs as an employer. This guide breaks down the full 2025/2026 NI system band by band, and includes a free calculator so you can get your exact figure for any employment type.
📑 Table of Contents
Free UK National Insurance Calculator
🧮 Free UK National Insurance Calculator
Select your employment type — employee, employer, or self-employed — enter your annual salary or profit, and choose your NI category letter. The calculator instantly shows your total NI, a full band-by-band breakdown, and weekly, monthly, and annual figures.
📋 2025/2026 National Insurance Rates at a Glance
| Class | Who Pays | Threshold | Main Rate | Above UEL / No Limit |
|---|---|---|---|---|
| Class 1 | Employee | £12,570 – £50,270 | 8.00% | 2.00% above £50,270 |
| Class 1 (Secondary) | Employer | Above £5,000 | 15.00% | 15.00% (no upper limit) |
| Class 4 | Self-Employed | £12,570 – £50,270 | 6.00% | 2.00% above £50,270 |
| Class 2 | Self-Employed (voluntary) | N/A | £3.45/week flat | — |
🔑 Key National Insurance Terms Explained
- Primary Threshold (£12,570): The point at which employees start paying NI — matched to the Income Tax personal allowance.
- Upper Earnings Limit / UEL (£50,270): Above this point, the employee NI rate drops from 8% to 2%, since NI is designed to fund contributory benefits rather than act as a pure income tax.
- Secondary Threshold (£5,000): The point at which employers start paying NI on an employee's earnings — notably lower than the employee threshold, and with no reduction above any upper limit.
- Class 4 (Self-Employed): Charged on annual trading profits using the same threshold structure as employee NI, but at lower rates (6% / 2% instead of 8% / 2%).
🧾 Worked Example: £35,000 Salary (Employee)
| Step | Calculation | Amount |
|---|---|---|
| Gross salary | — | £35,000 |
| NI-free allowance | Primary Threshold | £12,570 |
| Earnings in main band | £35,000 − £12,570 | £22,430 |
| NI at main rate | £22,430 × 8% | £1,794.40 |
| Earnings above UEL | Salary is below £50,270 | £0 |
| Total employee NI | Annual / Monthly | £1,794.40/yr (≈£149.53/mo) |
Separately, the employer would pay 15% on earnings above the £5,000 Secondary Threshold: (£35,000 − £5,000) × 15% = £4,500/year — an employer cost that's entirely on top of the employee's own deduction, and isn't visible on the employee's payslip.
💼 Self-Employed: Class 4 & Class 2
Self-employed workers pay Class 4 NI on trading profits, using the same threshold pattern as employees but at reduced rates: 6% on profits between £12,570 and £50,270, and 2% above that. Since April 2024, Class 2 NI became voluntary for most self-employed people — those with profits above the Small Profits Threshold no longer have to pay it automatically. It can still be paid voluntarily at a flat £3.45/week (£179.40/year) to protect State Pension entitlement and access to certain contributory benefits, which matters most for those with lower profits or gaps in their contribution record.
🏢 Employer NI & the Employment Allowance
Employers pay Class 1 Secondary NI at 15% on each employee's earnings above the £5,000 Secondary Threshold, with no upper earnings limit — unlike employee NI, this rate never drops. Many small employers, however, can reduce this cost using the Employment Allowance, worth up to £10,500 per year, which offsets employer NI liability directly. Eligibility rules apply — generally employers whose prior year employer NI bill was under £100,000 qualify, though certain business types and single-director companies face restrictions.
⚠️ Important Notes
- NI thresholds and Income Tax thresholds are calculated completely separately — don't assume one automatically lines up with the other.
- Workers over State Pension age stop paying employee or self-employed Class 4 NI entirely, even if they continue working — but employers still pay employer NI on their earnings regardless of age.
- Class 2 NI became voluntary for most self-employed people from April 2024, though paying it can still protect State Pension entitlement.
- Small employers may qualify for the Employment Allowance, reducing employer NI liability by up to £10,500/year.
❓ Frequently Asked Questions
National Insurance is a UK payroll deduction that funds state benefits including the State Pension, Jobseeker's Allowance, and Maternity Allowance. Employees, employers, and self-employed workers each pay different classes of NI depending on earnings and employment status.
Employees pay 0% up to £12,570, 8% on earnings between £12,570 and £50,270 (the Upper Earnings Limit), and 2% on earnings above £50,270.
Employers pay Class 1 Secondary NI at 15% on each employee's earnings above the £5,000 Secondary Threshold, with no upper limit. Many small employers can reduce this using the Employment Allowance, worth up to £10,500 per year.
Self-employed workers pay Class 4 NI at 6% on profits between £12,570 and £50,270, and 2% above that. Class 2 NI is no longer compulsory from April 2024 for most, though voluntary contributions of £3.45/week can protect State Pension entitlement.
No. Once State Pension age is reached, employee or self-employed Class 4 National Insurance stops, even if you continue working. Employers, however, still pay employer NI on your earnings regardless of your age.
No. Income Tax and National Insurance are calculated separately, using different thresholds and rates, and both are usually deducted from pay under PAYE. NI specifically builds entitlement to contributory benefits like the State Pension, while Income Tax has no such link.
Pair this with the UK Income Tax calculator for a complete payslip picture.
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📚 References
Rates and thresholds referenced in this article are based on official HMRC guidance and are updated periodically:
- GOV.UK — National Insurance
- GOV.UK — Rates and Thresholds for Employers 2025–2026
- GOV.UK — Employment Allowance
- QuinetCalc UK National Insurance Calculator — live calculator used in this article
This article is for general informational purposes only and does not constitute tax or financial advice. Actual NI deductions may vary based on category letter, multiple employments, or director's NI rules — consult HMRC or a certified payroll professional for personalized guidance.
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