Late January can be stressful if you've suddenly realised you need to file a tax return though haven’t told HMRC. This situation is more common than you think, especially for first-time taxpayers or those returning to Self Assessment after the Christmas break.
Knowing what action to take to avoid penalties and interest is vital. This guide provides clear tips on late tax return notification to help you navigate this situation quickly and correctly.
When do You Need to Notify HMRC?
In most cases, you must notify HMRC that you are liable to Income Tax or Capital Gains Tax by 5 October following the end of the tax year.
An Example
You make a capital gain from the disposal of cryptocurrency in 2024–25, you had until 5 October 2025 to notify HMRC. As a result, HMRC issues a formal notice to file a tax return.
Your return is due by the later of:
Missing the 5 October deadline can trigger penalties. However, taking action quickly can significantly reduce your exposure.
What action should I take if I discover an issue in late January?
If it’s late January and you've missed the notification deadline, do not panic. Instead, act immediately and take the following steps:
As a result of paying the correct tax liability by the deadline, you reduce the risk of penalties based on ‘potential lost revenue’.
An overview of how HMRC Charges Penalties
HMRC applies penalties based on:
Penalty ranges:
No penalty may be charged if:
What to do Once Registered for Self-Assessment
Once you've registered for Self-Assessment, submit your tax return as soon as practicable. This avoids further penalties for late filing.
The filing deadline then becomes the later of: 31 January following the tax year, or three months after HMRC issues the notice to file.
However any delays beyond these deadlines may result in a £100 fixed penalty or daily penalties after three months. Furthermore HMRC have the power to charge higher tax-geared penalties for longer delays
Special Steps if you've Previously been in Self Assessment
If you've previously been registered in Self Assessment you must reactivate your account.Do not register again. This may delay processing and could lead to incorrect tax calculations.
Therefore, you should reactivate your existing Self Assessment record by calling the Agent Dedicated Line, or completing form SA1. As you’ll already have a Unique Taxpayer Reference (UTR), this step is essential to avoid duplication.
Summary
Discovering in late January that you need to file a tax return can feel overwhelming. However, quick and informed action can prevent unnecessary penalties and interest.
Whether you are new to Self Assessment or returning after a break, following these tips on late tax return notification gives you the best chance of staying compliant and minimising costs.
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