Do I Need to File Self Assessment UK 2025/26?
You need to file Self Assessment if any one of the triggers below applies to you in the 2025/26 tax year (6 April 2025, 5 April 2026). This page covers the triggers, deadlines, and what happens if you ignore it.
The triggers, you need Self Assessment if…
- You're self-employed with gross trading income over £1,000 (the trading allowance threshold)
- You have property income (rental, Airbnb, lodgers above Rent a Room) over £1,000 gross, or net property profit over £2,500
- You're a company director with untaxed income
- (Historic only) You earned over £150,000 from PAYE in 2023/24 or earlier. The PAYE-only filing threshold was removed entirely from 2024/25 onwards, so high earners with all income via PAYE no longer have to file Self Assessment just because of their salary.
- Your untaxed savings/investment income exceeds £10,000
- Your dividend income exceeds £10,000
- You have capital gains above the £3,000 annual exempt amount (2025/26)
- You earned foreign income requiring a return
- You receive Child Benefit and you (or your partner) earn over £60,000 (HICBC)
- You want to claim higher-rate pension tax relief not given automatically through PAYE
- You have any other untaxed income HMRC can't collect via PAYE
What if I'm not sure?
HMRC's online tool ("Check if you need to send a Self Assessment tax return") is free and takes 5 minutes. The calculator above also tells you, based on your side income.
If in doubt, file. Filing a return where you owe nothing is harmless. Failing to file when required is not.
Deadlines for 2025/26
| Action | Deadline |
|---|---|
| Register for Self Assessment (first-time filers) | 5 October 2026 |
| File paper return | 31 October 2026 |
| File online return | 31 January 2027 |
| Pay tax owed | 31 January 2027 |
| Second payment on account (if applicable) | 31 July 2027 |
Penalties for missing the deadline
| Lateness | Penalty |
|---|---|
| 1 day late | £100 (automatic, even if you owe £0) |
| 3 months late | £100 + £10/day for up to 90 days (max £900) |
| 6 months late | Above + 5% of tax owed (or £300, whichever is greater) |
| 12 months late | Above + another 5% (or £300) |
Late payment penalties are separate: 5% of unpaid tax at 30 days, 5% at 6 months, 5% at 12 months, plus interest at HMRC's rate (~7.75% currently).
How to register
- Go to gov.uk/register-for-self-assessment.
- Choose "self-employed" or "not self-employed" as appropriate.
- HMRC posts you a Unique Taxpayer Reference (UTR) within 10 working days.
- Set up Government Gateway online account (if you don't have one).
- You can then file at any time before 31 January.
Don't wait until January, the activation code arrives by post and takes a week.
How to file
Three options:
- HMRC's online return, free, fine for simple cases
- Software (FreeAgent, Coconut, GoSimpleTax, TaxScouts, etc.), £0 to ~£200/year, friendlier UX, often includes record-keeping
- Accountant, £150 to £500 typical for simple side hustle return, more for complex situations
FAQs
I owe £0, do I still need to file?
If you crossed any of the triggers above (e.g. £1,001 gross trading income), yes, even if your final tax bill is £0 after expenses. Failing to file attracts the £100 penalty regardless.
Can I de-register if I stop side hustling?
Yes. Tell HMRC by post or online once your gross income falls back under the trigger thresholds. You may still need to file a final return for the year you de-register.
What if I missed registering by 5 October?
Register now anyway. The £100 fixed penalty for late filing kicks in from 1 February. Late registration alone usually doesn't attract a penalty if you still file by the deadline.