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You need to complete a Self Assessment tax return if HMRC has not already collected all the tax you owe through PAYE. The most common triggers are being self-employed and earning more than £1,000, being a company director with untaxed income, receiving rental or dividend income above the relevant thresholds, owing Capital Gains Tax, or being liable for the High Income Child Benefit Charge. If none of these apply and all your tax is taken at source, you almost certainly do not need to file.
HMRC provides a free eligibility tool Check if you need to send a Self Assessment tax return on GOV.UK. If you’re unsure after reading this guide, run your details through it or speak to an accountant before the deadline.
HMRC estimates that more than 12 million people in the UK complete a Self Assessment tax return each year. If you’re eligible, you must file your return yourself or through an accountant and pay any tax due. Missing it triggers automatic penalties, so it’s worth confirming whether you meet the criteria.
Who needs to file a Self Assessment tax return?
You must send a Self Assessment tax return for the 2025/26 tax year if any of the following applied to you between 6 April 2025 and 5 April 2026:
- Self-employed as a sole trader and earned more than £1,000 (before expenses).
- A partner in a business partnership.
- A company director with income that wasn’t taxed at source (directors of non-profits who received no pay or benefits in kind are generally excluded).
- Received £2,500 or more in untaxed income for example tips, commission, or money from renting out a room.
- A landlord who earned more than £1,000 from renting out property (the property allowance covers gross income up to £1,000).
- Received dividend income above £10,000 before tax (note: the tax-free dividend allowance is now just £500, so smaller dividends may still be taxable even if they don’t require a return).
- Owe Capital Gains Tax for example from selling shares, a second property, or other chargeable assets.
- Liable for the High Income Child Benefit Charge i.e. you or your partner has an adjusted net income over £60,000 and one of you claims Child Benefit (the charge tapers between £60,000 and £80,000).
- Have taxable income from abroad, or are a non-resident with UK income (such as expats with UK rental or pension income).
- A trustee of a trust or a registered pension scheme.
- Received a P800 underpayment notice from HMRC that can’t be settled through your tax code.
- Your State Pension was your only income and it exceeded your Personal Allowance.
Important update: You no longer have to file a Self Assessment return solely because your income exceeds £100,000. That PAYE-only trigger was raised to £150,000 for 2023/24 and removed entirely from 2024/25. High earners only need to file if another reason on this list applies.
When is a Self Assessment tax return required?
A return is required for any tax year (6 April to 5 April) in which one of the triggers above applied to you. If your circumstances changed during the year you started a side business, became a landlord, or crossed the Child Benefit charge threshold you may have become eligible without realising it. You must register for Self Assessment by 5 October following the end of that tax year.
Self Assessment deadlines for 2025/26
For the 2025/26 tax year (6 April 2025 to 5 April 2026):
| Action | Deadline |
|---|---|
| Register for Self Assessment (if new) | 5 October 2026 |
| Paper tax return | 31 October 2026 |
| Online tax return | 31 January 2027 |
| Pay the tax you owe | 31 January 2027 |
If you’re filing for an earlier year, the online deadline is always 31 January following the end of that tax year.
What happens if you miss the Self Assessment deadline?
Penalties are automatic and stack up the longer you leave it:
- 1 day late: £100 fixed penalty applies even if you have no tax to pay or have already paid.
- 3 months late: £10 per day, up to a maximum of £900 (90 days), on top of the £100.
- 6 months late: a further penalty of 5% of the tax due or £300, whichever is greater.
- 12 months late: another 5% or £300, whichever is greater (higher in serious cases).
Separate late-payment penalties apply to tax you haven’t paid: 5% of the unpaid tax at 30 days, again at 6 months, and again at 12 months plus interest charged daily on both the tax and the penalties. A genuine reasonable excuse may allow you to appeal, but the safest course is to file and pay on time.
Do I need an accountant for Self Assessment?
You can file your own return directly through your HMRC online account, and for straightforward cases that’s often enough. An accountant becomes worthwhile when your situation is more complex: multiple income sources, rental property, capital gains, the Child Benefit charge, or claiming reliefs and allowances you might otherwise miss. A specialist will make sure your return is accurate, your tax is calculated correctly, and the deadline isn’t missed.
Get expert help with your Self Assessment
Self Assessment doesn’t have to be stressful. The Chartered tax advisers at IBISS & CO help individuals across England including the self-employed, landlords, directors and high earners file accurately and on time. Get in touch to check your eligibility and take the return off your plate.
Frequently Asked Questions
Do I need to complete a Self Assessment tax return if I'm employed and pay tax through PAYE?
Usually no if all your tax is collected through PAYE and you have no other untaxed income, you don’t need to file. You only need a return if a specific trigger applies, such as untaxed income over £2,500, rental income, capital gains, or the High Income Child Benefit Charge.
Do I need to file Self Assessment if I earn over £100,000?
Not automatically. The requirement to file solely because income exceeds £100,000 was removed from the 2024/25 tax year. You’d only need to file if you have another reason, such as untaxed income or a Capital Gains Tax liability.
What's the deadline for the 2025/26 Self Assessment tax return?
The online filing and payment deadline is 31 January 2027. If you need to register for the first time, do so by 5 October 2026; paper returns are due by 31 October 2026.
What happens if I file my Self Assessment late?
You’ll get an automatic £100 penalty the day after the deadline, rising with daily penalties after three months and further charges at six and twelve months, plus separate penalties and interest on any unpaid tax.
Muhammad Sufyan Moavia
Muhammad Sufyan Moavia, Chartered Tax Adviser and Fellow Chartered Certified Accountant at IBISS & CO.
He has 15 years experience in accounting and tax, advising individuals and business owners on personal tax, HMRC matters, IHT, CGT and tax planning.
Last review: July 2026
