Self Assessment Tax Return: A Complete Guide for 2024/25
If you are self-employed, a landlord, a company director, or earn income outside of PAYE, you will need to file a Self Assessment tax return with HMRC. This guide explains everything you need to know.
Written by: Ram Shah FCCA, Director of Ascot Accountancy — FCCA qualified with 15+ years advising individuals and businesses across London on UK tax.
Quick Summary
- Online Self Assessment deadline: 31 January each year
- Paper return deadline: 31 October each year
- Register by 5 October in your second year of trading
- Late filing penalty: £100 immediately, more after 3 months
- You can claim expenses to reduce your tax bill
Who Needs to File a Self Assessment Tax Return?
You must register for Self Assessment and file a tax return if, in the last tax year (6 April to 5 April), you were:
- Self-employed as a sole trader and earned more than £1,000
- A partner in a business partnership
- A company director (unless your only income is PAYE salary)
- Earning rental income from property
- Earning more than £100,000 from employment
- Earning income from abroad or investments
- Claiming Child Benefit while earning over £60,000 (High Income Child Benefit Charge)
- Receiving untaxed income such as tips or commission
Key Deadlines for 2024/25
| Deadline | Date |
|---|---|
| Register for Self Assessment | 5 October 2025 |
| Paper tax return filing deadline | 31 October 2025 |
| Online tax return filing deadline | 31 January 2026 |
| Pay any tax owed | 31 January 2026 |
| First payment on account | 31 January 2026 |
| Second payment on account | 31 July 2026 |
What Expenses Can You Claim?
Allowable expenses reduce your taxable profit and therefore your tax bill. Common allowable expenses for the self-employed include:
What Are the Penalties for Filing Late?
- ✕1 day late: £100 automatic penalty
- ✕3 months late: Additional £10 per day (up to £900)
- ✕6 months late: 5% of tax owed or £300 (whichever is greater)
- ✕12 months late: A further 5% of tax owed or £300
- ✕Plus interest on unpaid tax
How an Accountant Can Help
While you can file your own Self Assessment return, a qualified accountant can:
- Ensure you claim all allowable expenses (reducing your tax bill)
- Identify tax reliefs and allowances you may not know about
- Complete and submit your return accurately on your behalf
- Liaise with HMRC if there are any queries
- Help you plan your tax payments to manage cash flow
- Provide year-round advice, not just at tax return time
Need Help with Your Self Assessment?
Ascot Accountancy handles self assessment for individuals and businesses across London. FCCA qualified. Fixed fees. No surprises.
