How Income Tax is Calculated: A Complete Guide
Income tax is a fundamental part of the UK tax system, affecting both employees and self-employed individuals. Understanding how income tax is calculated can help you manage your finances more effectively and ensure you are paying the correct amount.
This guide explains:
- How income tax is calculated
- Taxable and non-taxable income
- Tax bands and rates for 2024/25
- Personal allowances and tax reliefs
- How self-employed and PAYE workers are taxed
1. What is Income Tax?
Income tax is a tax on money earned from various sources, including:
- Employment (wages, salary, bonuses, commission)
- Self-employment (profits from business activities)
- Rental income from properties
- Dividends from shares
- Savings interest (if above allowances)
- Pension income
Not all income is taxable. Some sources of income, such as certain state benefits and tax-free savings, are exempt from income tax.
2. How Income Tax is Calculated
Income tax is calculated in the following steps:
- Determine total taxable income (employment, self-employment, dividends, rental income, etc.).
- Deduct personal allowances (if applicable).
- Apply tax bands and rates based on the remaining taxable income.
3. Tax-Free Personal Allowance
The personal allowance is the amount of income you can earn before paying income tax.
- 2024/25 Personal Allowance: £12,570
- If your total income is below £12,570, you do not pay income tax.
- If your income exceeds £100,000, the personal allowance is reduced by £1 for every £2 earned over £100,000.
Example: If your income is £125,140 or more, your personal allowance is reduced to £0, meaning all income is taxable.
4. Income Tax Bands and Rates (2024/25)
| Income Bracket | Tax Band | Tax Rate |
|---|---|---|
| £0 – £12,570 | Personal Allowance | 0% |
| £12,571 – £50,270 | Basic Rate | 20% |
| £50,271 – £125,140 | Higher Rate | 40% |
| Over £125,140 | Additional Rate | 45% |
Important Note:
- Scotland has different tax bands, with more tax brackets.
- The higher rate threshold remains frozen at £50,270 until at least 2028, increasing tax for those whose wages rise with inflation.
5. Example of Income Tax Calculation
Example: Basic and Higher Rate Taxpayer
- Annual Salary: £60,000
Step 1: Apply Personal Allowance
- £60,000 – £12,570 = £47,430 taxable income
Step 2: Apply Tax Bands
| Taxable Income Bracket | Tax Rate | Tax Due |
|---|---|---|
| £12,570 – £50,270 | 20% | £7,540 |
| £50,271 – £60,000 | 40% | £3,892 |
| Total Tax Payable | £11,432 |
The total income tax owed is £11,432 for the year.
6. How Income Tax is Collected
For Employees (PAYE System)
If you are employed, tax is deducted automatically through PAYE (Pay As You Earn):
Employers calculate and deduct income tax and National Insurance before paying wages.
A tax code (e.g., 1257L) is used to determine allowances.
HMRC adjusts tax codes if circumstances change (bonuses, benefits, second jobs).
For Self-Employed Individuals (Self-Assessment Tax Return)
If you are self-employed, you must:
Report income and expenses through a self-assessment tax return.
Pay income tax and National Insurance by 31 January (first payment) and 31 July (second payment on account, if applicable).
Register for Self-Assessment – HMRC
7. Additional Tax Considerations
National Insurance Contributions (NICs)
- Employees and self-employed individuals also pay National Insurance, which funds state pensions and benefits.
- Employee NICs:
- 8% on earnings between £12,570 – £50,270
- 2% on earnings above £50,270
- Self-Employed NICs:
- Class 2: £3.45 per week if profits exceed £12,570
- Class 4: 6% on profits between £12,570 – £50,270 and 2% on profits above £50,270
National Insurance Contributions – HMRC
Dividend Tax Rates
If you receive dividends from shares, a separate tax rate applies:
| Dividend Income | Tax Rate |
|---|---|
| First £500 | 0% (Dividend Allowance) |
| Basic Rate (Up to £50,270) | 8.75% |
| Higher Rate (£50,271 – £125,140) | 33.75% |
| Additional Rate (Over £125,140) | 39.35% |
8. How to Reduce Your Income Tax Bill
Increase Pension Contributions – Contributions to workplace or private pensions reduce taxable income.
Claim Work-Related Expenses – If self-employed, business expenses lower taxable profit.
Use ISA Savings – Interest earned in ISAs (Individual Savings Accounts) is tax-free.
Gift Aid Donations – Charitable donations receive tax relief at 20%, 40%, or 45%.
Marriage Allowance – If one spouse earns below £12,570, they can transfer £1,260 of unused allowance to a higher-earning spouse.
Tax-Free Savings and Investments – HMRC
9. Summary: Understanding Your Income Tax Bill
- Everyone has a £12,570 tax-free personal allowance (unless earning over £100,000).
- Tax rates are 20% (basic), 40% (higher), and 45% (additional).
- PAYE employees have tax deducted automatically, while self-employed individuals must file a tax return.
- National Insurance Contributions (NICs) apply separately to income tax.
- Tax reliefs and allowances, such as pension contributions and ISA investments, can reduce taxable income.
Self-Assessment Tax Returns – HMRC
Need Tax Advice?
Merranti Accounting provides expert tax support, helping you understand your tax liability, claim the right allowances, and reduce your tax bill.
Contact us today to ensure you are managing your income tax efficiently.
