Published:
21
Oct
2012
Updated:
24
Nov
2025
Written by
Ray Coman
When to register, how to register and what to do if you are late are among the most common concerns when it comes to the self-assessment. In response to frequently asked questions, the following guide offers a brief overview on the topic of registration for self-assessment.
1. Do I need to complete a Self-Assessment Tax Return?
2. When must I notify HMRC?
3. What happens if I notify HMRC late?
4. What are the filing and payment deadlines?
5. What are the penalties if I file or pay late?
6. How long does it take to receive a UTR?
7. HMRC have never contacted me — how can I be late?
8. HMRC told me something different on the phone. What should I rely on?
9. What should I do if I have realised this late?
10. Assistance
1. Do I need to complete a Self-Assessment Tax Return?
The question is less about “being self-employed” and more about whether any part of your income falls outside what PAYE can sensibly deal with.
You would need to register for Self Assessment if any of the following apply:
Self-employment or trading activity
If you carry on a trade (even at a modest level) and your gross receipts exceed the £1,000 Trading Allowance, you fall into Self Assessment. Partners in a partnership register individually. This has not changed.
Property income
Any form of rental income (UK or overseas) needs to be reported. Joint ownership is assessed by reference to your share, not the property as a whole.
Untaxed or only partly taxed income
PAYE can deal with straightforward employment income, but does not collect tax on:
- dividends and investment income above allowances
- interest above the Savings Allowance
- foreign income, pensions or gains
- benefits-in-kind not fully captured by your tax code
- trust or estate income
- cryptoasset transactions
- casual or miscellaneous income
These all require a Tax Return.
Capital gains
A return is required if your gains exceed the annual exemption, or if the total proceeds exceed four times that exemption, even where the gains themselves are small. This commonly arises with share disposals and second properties. For more complex positions, refer also to the guidance on capital gains tax returns.
5. PAYE income above a threshold — the rule that no longer applies
For many years HMRC required a Tax Return if your employment income exceeded £100,000 (increased to £150,000 from 2023/24). This requirement was abolished from the 2024/25 tax year for those whose income is fully taxed through PAYE and who have no other sources of income. Untaxed or complex income will still give rise to a requirement. Many high earner will still need to do a Tax return because, for instance, they have bank interest.
Employment expenses
If your employment expenses exceed £2,500, HMRC generally requires a Tax Return to process the claim properly. The simpler “P87 route” applies only below that level.
Trust income
Trust or settlement income remains a standalone trigger. Even modest trust income requires a Self-Assessment return.
If none of the above applies, and you receive only employment or pension income fully taxed at source, you may not need a tax return.
When must I notify HMRC?
The deadline is 5 October following the end of the tax year in which the liability first arose. If, for example, your rental income began during 2024/25, you should notify HMRC by 5 October 2025. While this is the strict position, provided you have a UTR by the filing deadline (usually of 31 January following the end of the tax year), there is no negative repercussion to registering after 5 October. It is a common misconception that HMRC will write to the taxpayer first. In fact, the obligation works in the opposite direction: the taxpayer must tell HMRC.
What happens if I notify HMRC late?
Late notification is treated under the “failure to notify” regime. The penalty depends on:
- the amount of tax unpaid at the time you should have notified
- whether the behaviour was deliberate or simply oversight
- whether you disclosed the issue voluntarily
- the degree to which you co-operate in establishing the correct position
In practice, where the tax is paid in full by 31 January, penalties are often significantly reduced, and in many routine cases nothing further arises provided the return is then filed. Nevertheless, the legal position remains that HMRC may charge a penalty.
What are the filing and payment deadlines?
31 January: online tax return filing deadline
31 January: balancing payment for the year
31 July: second payment on account (if relevant)
31 October: paper return deadline
If HMRC issues a notice to file during the year, the deadline becomes three months from the date of the notice.
What are the penalties if I file or pay late?
The late-filing penalties are structured and do not depend on the amount of tax:
- 1 day late: £100
- 3 months late: £10 per day (up to £900)
- 6 months late: further 5% of tax due
- 12 months late: further penalties depending on behaviour
Late-payment penalties apply at 30 days, 6 months, and 12 months (each at 5% of the unpaid tax) and interest runs from the due date.
How long does it take to receive a UTR?
HMRC typically issues a Unique Taxpayer Reference within a few weeks, though the timeframe can lengthen in December and January. You cannot file online without it, so early registration avoids unnecessary compression near the deadline.
HMRC does not need to issue a notice before penalties can apply. The obligation to notify rests with the taxpayer. Many enquiries begin when HMRC receives third-party information (for example, employer records, interest statements, or property data) that indicates a return was required.
HMRC told me something different on the phone. What should I rely on?
Telephone guidance can be helpful for simple points, but it is not determinative. HMRC staff do not give tailored tax advice, and informal guidance cannot override legislation. Written guidance or a properly analysed tax position is more reliable, particularly if penalties or disclosure issues are involved.
What should I do if I have realised this late?
Register without delay, file the return as soon as the UTR arrives, and pay any tax due. Most late-notification cases resolve cleanly once the position is disclosed, especially if the tax is paid promptly and the behaviour is non-deliberate.
Assistance
If you need to register, prepare a Return, deal with past years or clarify the position, we can handle this and outline the tax exposure, deadlines and procedural steps.
Contact us if you would like to proceed.