If you’re self-employed or a sole trader, submitting a Self-Assessment tax return is a legal requirement. Unlike traditional employees—whose income tax is automatically deducted through PAYE—you’re responsible for calculating and paying your own taxes.
It can be tempting to juggle everything yourself, but accounting often falls by the wayside. This leads to last-minute stress or even missed deadlines, which can result in penalties from HMRC.
Do You Need to File a Self-Assessment Tax Return?
According to HMRC, you must file a tax return for the 2024/25 tax year (6 April 2024 – 5 April 2025) if:
- You earned more than £1,000 from self-employment (before tax relief)
- You were part of a business partnership
- You had to pay Capital Gains Tax (e.g. after selling an asset)
- You were liable for the High-Income Child Benefit Charge
- You had untaxed income (e.g. rental income, savings interest, dividends)
If you’re unsure, you can check on the GOV.UK website or speak with a personal tax accountant at Oasis for clarity.
How Much Tax Will You Need to Pay?
As a sole trader, you only pay tax on your profits, not your total income. Here’s what you need to know:
- Personal Allowance (2024/25): £12,570 tax-free
- Income Tax: Paid on profits above this threshold at the standard tax bands
- National Insurance:
- Class 2: Due if profits are £6,725+
- Class 4: Due if profits are £12,570+
These contributions go towards benefits like the State Pension. Keeping accurate financial records throughout the year makes calculating this much easier.
When Should You Register?
If you’re newly self-employed, you must register for Self-Assessment by 5 October 2025. If you’ve filed before but skipped a year, you’ll need to reactivate your account.
To register, you’ll need your National Insurance number and basic details. HMRC will send you a Unique Taxpayer Reference (UTR), which you’ll use for all correspondence.
How to Prepare for Your Tax Bill
Don’t wait until January. Preparation should start the moment you earn your first income:
- Keep every receipt and invoice
- Consider using accounting software
- Open a business bank account to separate finances
- Save 25–30% of each payment to cover tax and NI
You may also be required to make payments on account if your bill exceeds £1,000—essentially paying part of next year’s tax in advance.
How to File Your Self-Employed Tax Return
There are two ways to file your tax return:
1. Online via HMRC (Recommended)
- Easier and faster
- Deadline: 31 January 2026
- Automatically calculates your tax
- Immediate confirmation of submission
2. By Post
- Deadline: 31 October 2025
- Slower and more manual
Filing early helps you budget, reduces stress, and gives time to set up a payment plan if needed. HMRC also offers a Time to Pay service, which can spread your tax bill over 12 months.
What Happens If You Miss the Deadline?
Penalties for late filing are harsh—even if you owe no tax:
- £100 fine immediately after missing the deadline
- £10/day fine after 3 months (up to £900)
- 5% or £300 (whichever is greater) after 6 months
- A second 5% or £300 charge if 12 months late
You Can Appeal If:
- A close relative died just before the deadline
- You were seriously ill or hospitalised
- Your software or HMRC’s systems failed
- You suffered a fire, flood, or theft
- Postal delays outside your control
- Your accountant failed to submit on your behalf
Appeals must be made within 30 days of your penalty notice. Learn more on GOV.UK.
Key Deadlines for Your 2024/25 Tax Return
To avoid late filing penalties and ensure you stay on top of your tax responsibilities, make a note of these important dates:
Missing these deadlines can result in fines—even if no tax is due—so setting calendar reminders is a smart move.
How Oasis Accountants Can Help
At Oasis Accountants, we understand the pressures of running your own business—and how confusing tax deadlines can be.
Our personal tax accountants are here to help you:
- Stay compliant and avoid fines
- Maximise your allowable expenses
- File your return correctly and on time
- Plan ahead for future tax bills
Contact us today to book your free 30-minute consultation or call us on 020 3818 9530.
Let us take care of your tax return—so you can focus on doing what you do best.
