HMRC uses the system of self-assessment to collect Income Tax from taxpayers who fulfil certain criteria. By filing a self-assessment tax return, you report the details of your taxable income and gains for the tax year and pay tax. One of the fundamentals of the self-assessment process is knowing: How soon should you submit your self-assessment tax return? This blog will discuss the essentials involved in filing a self-assessment tax return so you can avoid HMRC penalties and ensure compliance with tax rules.
When Do You Do Self-Assessment?
HMRC self-assessment is a tax collection process by which HMRC reviews your taxable income, profits, and expenses throughout the tax year. By using this system, HMRC reviews how much tax you owe for the tax year. You can file your tax return (also called an SA100) through three methods: online, on paper, or via a third-party agent.
There are several HMRC supplementary forms you might require to attach to the main SA100 tax return, depending on your income source. Find out what form you need to complete and submit:
How Soon Should You Submit Your Self-Assessment Tax Return?
A tax year in the UK runs from the 6th of April to the following 5th of April. So, the 2025/26 tax year started on 6 April 2025 and would end on 5 April 2026.
Now, for the tax, you can submit your self-assessment return for a certain tax year from the day after that tax year finishes. For instance, since the 2025/26 tax year ends on 5 April 2026, you can file your Self Assessment tax return for this year starting from 6 April 2026 onwards.
Learning Important Self-Assessment Tax Return Deadlines
If you are required to submit a self-assessment tax return each year, you must remain heedful of the following important dates and deadlines during the tax year to ensure you do not miss them:
- 5 October – Deadline For Self-Assessment Registration
- 31 October – Deadline To Submit A Paper Tax Return
- 30 December – Deadline For Paye Tax Collection
- 31 January – Deadline To File The Online Return And Pay Tax Bill
- 31 January – Deadline To Make First Payment On AccountÂ
- 31 July – Second Payment On Account
Can You Submit Your Tax Return Early?
Yes, you can complete and submit your self-assessment tax return early because it can benefit you in different ways, including
Early Tax Refunding
By submitting your tax return earlier, you can find out sooner if HMRCÂ owes you a refund. As a result, you will get the refund sooner, which can certainly enhance your cash flow.
Claiming Benefits
Filing your tax return early gives legal proof of your business income, which you can use to apply for a mortgage, loan or claim benefits.
To know when to do a self-assessment, you must first determine whether or not you meet HMRC’s criteria to register for a self-assessment tax returnÂ
Avoiding Mistakes
HMRC strictly enforces self-assessment tax returns. Submitting an accurate tax return not only keeps you fully compliant but also helps you avoid potential penalties, which can range from 0% to over 30% of the tax owed if HMRC identifies an error first. If you are filing your tax return earlier, you can have sufficient time to assess the return and ensure there are no errors.
Avoiding The Last-Minute Rush
As the submission deadline for the self-assessment tax return nears, many taxpayers rush to file, leading to significant congestion on the HMRC website, causing technical errors. Therefore, it is advisable to have ample time and submit your return in advance to avoid unforeseen complications.
What Are HMRC Penalties For Late Filing Of A Self-Assessment Tax Return?
Staying aware of how soon should you submit your Self-Assessment tax return is also important because submitting and paying your tax bill on time lets you avoid HMRC’s late-filing and late-payment penalties. Meeting deadlines ensures a smooth, compliant tax process.
Penalties for Late Registration
If you register by 5 October and pay your tax bill by 31 January, you can easily avoid HMRC’s ‘failure to notify’ penalty. You might be penalised within 12 months after you have submitted your tax return to HMRC, based on the amount you still owe on your tax return.
Penalties for Sending Late Returns
By avoiding late returns, you are avoiding the following penalties.
- A £100 instant fine at the time of missing the January 31st deadline
- A £10-per-day penalty, if you have not filed the return after 3 months, up to a maximum of £900 (i.e., by April 30th of the following year)
- A £300 fine (or 5% of the tax you owe – whichever is greater) if it still hasn’t been filed for another 90 days (after 6 months).
- Another £300 fine (or 5% of the tax due – whichever is greater) in case you fail to file it in the next year as well (after 12 months).
- Additional penalties of up to 100% of the total tax owed if the HMRC assumes you intentionally avoid paying tax.
Therefore, you can avoid the inconvenience of HMRC penalties by filing your tax return at an earlier date.
Bottom Line
Knowing the answer to the question, How soon should you submit your Self-Assessment tax return, is a significant part of filing your tax return. Staying aware of the self-assessment deadlines can help you avoid HMRC penalties and get a clearer picture of financial obligations and tax reliefs you can claim.
Nevertheless, if you are more focused on core business operations and are short on time to file your tax return, seeking help from a qualified personal tax accountant is immensely helpful. They will ensure your self-assessment tax returns are filed accurately and on time, so compliance is not an inconvenience for you. Alternatively, you can get the error-free online self-assessment services to file your tax return ahead of time.
FAQs
What happens if I miss the self-assessment deadline?
Meeting HMRC deadlines for completing your self-assessment tax return is essential since non-compliance leads to penalties.
What happens if I make a mistake on my self-assessment?
If you file your tax return earlier than the 31 January deadline, you can have sufficient time to assess the return and ensure there are no errors. Furthermore, you would also have more time to seek professional advice in case any confusion arises regarding the tax filing that you might find difficult to resolve yourself.
What is the deadline to register for self-assessment with HMRC?
If you need to complete a tax return for the previous tax year and you have not filed one before, it is crucial that you tell HMRC by 5 October. Notably, in order to tell HMRC, you must register for self-assessment with HMRC by 5 October.
