Becoming self-employed is an exciting step — whether you’re starting a freelance business, offering consulting services, or running an online shop. But one thing many people don’t realise is that there are strict deadlines to notify HM Revenue & Customs (HMRC).
Missing this deadline can lead to penalties — even if your income is small or irregular.
In this post, we’ll break down when you need to register, what happens if you’re late, and give some realistic examples to help you understand the consequences.
When You Need to Register with HMRC
The UK tax year runs from 6 April to 5 April.
If you become self-employed at any point during the tax year, you must notify HMRC by 5 October following the end of that tax year.
Example:
- You start trading on 1 June 2025 (2025/26 tax year).
- You must notify HMRC by 5 October 2026.
You can register through your HMRC online account or by calling their helpline if needed.
Even if your profits are low, you still need to register if you’re carrying out a trade or business. If your total self-employment income is under the trading allowance of £1,000, you may not need to file a return, but you still need to assess your position carefully.
What Happens If You Miss the Deadline?
If you don’t register on time, HMRC may charge a failure to notify penalty under Finance Act 2008 Sch 41.
The penalty depends on:
- How late the notification is
- Whether the failure was careless, deliberate, or deliberate and concealed
- Whether you told HMRC before they contacted you (unprompted disclosure)
| Failure Type | Prompted Disclosure | Unprompted Disclosure |
| Careless | 0%–30% | 0%–30% |
| Deliberate | 20%–70% | 20%–70% |
| Deliberate & concealed | 30%–100% | 30%–100% |
Note: If no tax is due, HMRC will often not charge a penalty, but it’s still important to notify them as soon as possible.
Real-Life Examples
Example 1: Genuine Mistake – Careless
Amira started working as a self-employed graphic designer in June 2024 but thought she only had to tell HMRC when she filed her tax return. She realised her mistake in December 2025 and notified HMRC herself.
- She was 2 months late.
- HMRC accepted it was a careless mistake and unprompted disclosure.
- A small penalty (or no penalty) may apply, especially if tax due is low.
Example 2: Deliberate Delay – Deliberate
James began trading as a consultant in May 2023 but deliberately didn’t register to “wait and see how it goes.” HMRC opened an enquiry in late 2025.
- This was a deliberate failure and prompted disclosure.
- He owed £2,000 in tax for the first year.
- Penalty rate could be between 20% and 70%, so he may pay an additional £400–£1,400 in penalties, plus interest.
Example 3: No Tax Due
Sophie started selling handmade items in February 2025 but earned under £1,000 for the year. She realised later she should have registered but contacted HMRC immediately.
- As no tax was due and she came forward voluntarily, no penalty was charged.
Final Thoughts
Starting self-employment gives you flexibility and independence, but it also comes with legal tax responsibilities.
Key takeaway:
- Register by 5 October after the end of the tax year you started.
- If you miss the deadline, contact HMRC as soon as possible.
- The faster you act, the lower the risk of penalties.
If you’re unsure whether you need to register or how to do it, it’s best to get advice early — it can save you money and stress later.
Need help?
Many people unintentionally miss the HMRC deadline in their first year of self-employment. A tax adviser can guide you through registration, record-keeping, and filing to stay compliant and penalty-free.
