*Calculations based on 2025/26 tax year thresholds announced in Autumn 2024 Budget.
function calculateNI() {
var incomeInput = document.getElementById('incomeAmount').value;
var payPeriod = document.getElementById('payPeriod').value;
var niCategory = document.getElementById('niCategory').value;
if (incomeInput === "" || isNaN(incomeInput)) {
alert("Please enter a valid income amount.");
return;
}
var grossIncome = parseFloat(incomeInput);
var annualIncome = 0;
// Normalize to Annual Income for Calculation
if (payPeriod === 'weekly') {
annualIncome = grossIncome * 52;
} else if (payPeriod === 'monthly') {
annualIncome = grossIncome * 12;
} else {
annualIncome = grossIncome;
}
var annualNI = 0;
// 2025/26 Thresholds and Rates
// Data based on Autumn Budget 2024 announcements for April 2025 start
if (niCategory === 'employee') {
// Class 1 Employee NI (Standard Category A)
// Primary Threshold (PT): £12,570
// Upper Earnings Limit (UEL): £50,270
// Rate PT to UEL: 8% (Main rate cut in 2024, maintained 2025)
// Rate above UEL: 2%
var pt = 12570;
var uel = 50270;
var mainRate = 0.08;
var upperRate = 0.02;
if (annualIncome > uel) {
annualNI = ((uel – pt) * mainRate) + ((annualIncome – uel) * upperRate);
} else if (annualIncome > pt) {
annualNI = (annualIncome – pt) * mainRate;
} else {
annualNI = 0;
}
} else if (niCategory === 'self_employed') {
// Class 4 Self-Employed NI
// Lower Profits Limit: £12,570
// Upper Profits Limit: £50,270
// Rate LPL to UPL: 6% (Main rate cut)
// Rate above UPL: 2%
var lpl = 12570;
var upl = 50270;
var class4MainRate = 0.06;
var class4UpperRate = 0.02;
if (annualIncome > upl) {
annualNI = ((upl – lpl) * class4MainRate) + ((annualIncome – upl) * class4UpperRate);
} else if (annualIncome > lpl) {
annualNI = (annualIncome – lpl) * class4MainRate;
} else {
annualNI = 0;
}
// Note: Class 2 is effectively abolished/voluntary for most, excluded for simplicity.
} else if (niCategory === 'employer') {
// Class 1 Secondary (Employer NI)
// Major Change in 2025 Budget
// Secondary Threshold: Reduced to £5,000
// Rate: Increased to 15%
var st = 5000;
var employerRate = 0.15;
if (annualIncome > st) {
annualNI = (annualIncome – st) * employerRate;
} else {
annualNI = 0;
}
}
// Output formatting
var monthlyNI = annualNI / 12;
var weeklyNI = annualNI / 52;
var effectiveRate = 0;
if (annualIncome > 0) {
effectiveRate = (annualNI / annualIncome) * 100;
}
// For employer, take home isn't relevant in the same way, but cost basis is.
// For simplicity, we calculate income minus NI cost for the 'Take Home' slot,
// though for Employers this implies "Gross Pay remaining" isn't quite right contextually,
// but standardizes the UI.
var takeHomeVal = annualIncome – annualNI;
if(niCategory === 'employer') {
document.getElementById('takeHome').parentElement.style.display = 'none'; // Hide take home for employer view
} else {
document.getElementById('takeHome').parentElement.style.display = 'flex';
}
// Set DOM elements
document.getElementById('totalAnnualNI').innerText = '£' + annualNI.toLocaleString('en-GB', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('monthlyNI').innerText = '£' + monthlyNI.toLocaleString('en-GB', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('weeklyNI').innerText = '£' + weeklyNI.toLocaleString('en-GB', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('effectiveRate').innerText = effectiveRate.toFixed(2) + '%';
document.getElementById('takeHome').innerText = '£' + (takeHomeVal).toLocaleString('en-GB', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('results-area').style.display = 'block';
}
Understanding UK National Insurance Rates 2025/26
The 2025/26 tax year brings significant changes to the National Insurance (NI) landscape in the United Kingdom, following announcements made in the Autumn Budget 2024. Whether you are an employee, self-employed, or an employer, understanding these new rates is crucial for accurate financial planning.
Key Changes for April 2025
The most substantial changes for 2025 affect employers, while employee rates have seen stabilization following previous cuts.
Category
Threshold (Annual)
Rate (2025/26)
Employees (Class 1)
£12,570 – £50,270
8%
Employees (Higher Rate)
Over £50,270
2%
Employers (Class 1 Secondary)
Over £5,000 CHANGE
15% INCREASE
Self-Employed (Class 4)
£12,570 – £50,270
6%
For Employees (Class 1 Primary)
If you are an employee, your National Insurance contributions are calculated on your gross earnings. For the 2025 tax year:
0% Rate: You pay nothing on the first £12,570 you earn.
8% Main Rate: Earnings between £12,570 and £50,270 are taxed at 8%. This rate reflects the reductions made in previous fiscal updates.
2% Higher Rate: Any earnings above £50,270 attract a 2% contribution charge.
For Employers (Class 1 Secondary)
The 2025 financial year sees a significant increase in the cost of employing staff. The employer's NI rate has increased from 13.8% to 15%. Furthermore, the Secondary Threshold—the point at which employers start paying NI on an employee's salary—has been lowered from £9,100 to £5,000.
To mitigate this for smaller businesses, the Employment Allowance has increased to £10,500, allowing eligible businesses to reduce their annual NI liability.
For the Self-Employed (Class 4)
Self-employed individuals pay Class 4 NI on their profits. The main rate stands at 6% for profits between £12,570 and £50,270, with a 2% rate applied to profits exceeding the upper limit. Class 2 NI has effectively been abolished for most individuals, simplifying the tax return process.
How to Use This Calculator
Enter your gross income (before tax) and select your payment period. Ensure you select the correct "Employment Status" to apply the 2025 specific rules:
Select Employee to see deductions from your payslip.
Select Employer to calculate the business cost of a salary (excluding pension costs).
Select Self-Employed for Class 4 calculations on annual profit.