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If you’re self-employed, a landlord, or have other income that needs reporting, keeping track of the Self Assessment deadline is one of the simplest ways to avoid stress and unexpected HMRC penalties.
If you would rather someone else handled the return properly, our Cheap Tax Return accountants can help you get it sorted before the Self Assessment deadline.
Simple, transparent pricing with no surprises. Get expert help from qualified accountants and know exactly what you’ll pay before you start.
What Is The Self Assessment Deadline?
The Self Assessment deadline depends on what you are filing and how you submit it.
For most people, the important date is 31 January 2027. This is the deadline for submitting an online Self Assessment tax return for the 2025/26 tax year and paying the tax due.
The tax year covered by that return ended on 5 April 2026. So, if you searched for the ‘2026/27 Self Assessment deadline’, it is worth noting that the upcoming January 2027 deadline actually covers the 2025/26 tax year, while the actual 2026/27 return won’t be due until January 2028.
Also, you do not have to wait until January to file. HMRC allows you to submit your online return from 6 April 2026 onwards.
The dates can feel a bit confusing because you may need to register, file and pay at different times.
Here is the simple version.
| What you need to do | Deadline |
| Register for Self Assessment for 2025/26 | 5 October 2026 |
| Send a paper tax return | 31 October 2026 |
| Submit online tax return | 31 January 2027 |
| Pay your Self Assessment tax bill | 31 January 2027 |
| Pay through your PAYE tax code, if eligible | 30 December 2026 |
| Second payment on account, if required | 31 July 2027 |
The tax Self Assessment deadline that most people mean is 31 January 2027. Still, if this is your first return, 5 October 2026 may be the date that matters most right now.
When Is The Deadline To Register For Self Assessment?
Before you can even file a return, you have to tell HMRC that you actually need to do one. The official deadline to register for Self Assessment is 5 October 2026.
This normally applies if you need to file a return but:
- You have never sent a Self Assessment tax return before.
- You were registered in the past but did not need to file a return for the previous tax year.
- You became self-employed between 6 April 2025 and 5 April 2026.
- You started receiving other untaxed income that needs reporting.
Registering gives HMRC time to set up your account and issue your Unique Taxpayer Reference, usually called a UTR. Leaving it until the last minute can create a needless rush, especially if you need to gather records or reset account details.
If you miss the deadline to register for Self Assessment, HMRC may charge a failure-to-notify penalty. The amount can depend on the reason for the delay and how quickly you put things right.
When Is The Paper Self Assessment Deadline?
The paper Self Assessment deadline is 31 October 2026 for returns covering 2025/26.
HMRC must receive your paper return by the deadline on 31 October. Because it is a physical document, you should post it well in advance to ensure it arrives before the end of the day. Posting it on 31 October is risky, as the return needs to arrive by the deadline, not simply be sent on that date.
Most people now file online because the online deadline is three months later. Online filing also gives you an instant submission receipt, calculates the tax due and makes it easier to correct certain errors if needed.
If you missed the paper deadline, you can normally still submit online by 31 January 2027.
When Is The Online Self Assessment Deadline?
The online Self Assessment tax return deadline for 2025/26 is 11:59pm on 31 January 2027.
Your tax return needs to include income and gains from the tax year ending 5 April 2026. Depending on your situation, this could include:
- Self-employment income and allowable business expenses.
- Rental income from UK or overseas property.
- Company dividends.
- Salary or benefits not fully taxed through PAYE.
- Savings interest and investment income.
- Capital gains that need reporting through Self Assessment.
- Pension income, foreign income or other taxable earnings.
The tax return itself is only part of the job. Check the figures carefully, keep your records and make sure you can pay what is due. If something looks odd, it is much easier to sort out in November than at 10pm on 31 January.
At Cheap Tax Returns, we often find that clients who bring things together early have a far less stressful January. It also gives time to identify valid expenses and make sure nothing has been missed.
What Are The Main Self Assessment Payment Dates?
Paying your tax bill is separate from submitting the form, though the main deadline lands on the exact same day. You need to know these key Self Assessment payment dates:
- 31 January 2027: You pay any remaining tax owed for the 2025/26 tax year (the balancing payment). You also pay your first “payment on account” toward your 2026/27 bill if applicable.
- 31 July 2027: You pay your second “payment on account” toward your 2026/27 tax liability.
Payments on account are advance payments toward your next tax bill. HMRC sets each payment at roughly half of your previous year’s total bill. If your remaining Self Assessment tax bill is £1,000 or more, and less than 80% of your total tax is collected at source, these advance payments usually apply to you.
What Happens If You Miss the Self Assessment Deadline?
Missing a Self Assessment deadline can become expensive. HMRC can apply late filing penalties if your return is submitted after the deadline. Interest and late payment penalties can also apply if your tax remains unpaid.
Late Filing Penalties
| Delay | Penalty |
| 1 day late | An automatic £100 penalty applies the moment you miss the 31 January deadline, even if you owe no tax or are due a refund |
| Over 3 months late | Additional daily penalties of £10 per day apply for up to 90 days (a maximum of £900). |
| 6 months late | A further charge of 5% of the tax due or £300, whichever is higher. |
| 12 months late | Another charge of 5% of the tax due or £300, whichever is higher. Severe cases involving deliberate concealment can attract higher penalties up to 100% of the tax owed. |
Penalties can apply even when no tax is owed.
Late Payment Penalties and Interest
- Unpaid tax interest: Interest accumulates on any outstanding tax bill starting from 31 January until the amount is fully paid.
- 30 days late after the due date: A penalty of 5% of the unpaid tax is charged.
- 6 and 12 months late: Additional 5% penalties apply if the tax remains unpaid at those intervals
The longer payment remains overdue, the more costs can build up.
Want to know exactly what you could be charged? We have covered the penalties, interest and different late-payment scenarios in our detailed guide to Self Assessment penalties.
How Can You Avoid Missing The Self Assessment Deadline?
Nothing clever. Just a few habits.
- Register now if you haven’t
- Gather your records: invoices, bank statements, P60, rental figures, interest and pension statements
- File by December. January is when HMRC’s online service gets busy
- Set aside a slice of every payment you receive for the tax bill
- Put all five dates in your diary
Not sure where to start? Send your figures to Cheap Tax Returns and we will tell you what you owe and by when.
Frequently Asked Questions
What is the Self Assessment deadline for 2026/27?
For the 2025/26 tax return filed during the 2026/27 tax year, the online filing and payment deadline is 31 January 2027. The paper return deadline is 31 October 2026.
Is 31 January 2027 the deadline for the 2026/27 tax year?
No. The 2026/27 tax year runs from 6 April 2026 to 5 April 2027, and its return opens on 6 April 2027. The Self Assessment deadline for that one is 31 January 2028 for online filing and payment. Paper returns are due 31 October 2027. If it is your first year of self-employment, register by 5 October 2027.
What if I cannot afford to pay my tax bill by 31 January?
Contact HMRC immediately to set up a “Time to Pay” arrangement. Setting up an instalment plan before the payment cutoff helps you avoid additional late payment penalties, though interest will still accrue on late balances.
Can I file my tax return before the Self Assessment deadline?
Yes, and you should if you can. The 2025/26 return has been open since 6 April 2026. You can file any day from then until 31 January 2027. Filing early gives you months to plan your finances, and you still do not have to pay the tax bill until 31 January 2027.
Do I need to file a tax return if I made a financial loss?
Yes, you should still file. Reporting a business loss lets you offset that loss against future profits or other income, reducing your overall future tax bills.
Need a Hand With Your Tax Return?
At Cheap Tax Returns, we file Self Assessment returns for people just like you, from first-time sole traders to landlords with a couple of properties.
If you are unsure about your filing date, payments on account or what information you need to provide, getting things checked before the Self Assessment deadline can make the process much less stressful.
Get in touch with us today and send your figures. We will check what you owe, spot any payments on account and get your return in well before 31 January.
Our experts handle your tax return properly the first time, making sure everything is filed correctly and on time so you never worry about HMRC again.
The Bottom Line
The Self Assessment deadline most taxpayers need to remember is 31 January 2027 for the 2025/26 tax year. But there are earlier dates worth knowing, particularly 5 October for registration and 31 October for paper returns.
If you are self-employed, have property income or receive other income that needs to be reported, check your position early. A few weeks before the deadline is not the ideal time to start looking for old invoices and bank statements.
If your tax position is messy, you are behind with records, or you just want someone else to handle the return properly, Cheap Tax Returns can help you get it sorted before the Self Assessment deadline.
