The Self Assessment tax return covers income earned during the 2025–26 tax year, which runs from 6 April 2025 to 5 April 2026.
Missing a filing or payment deadline can result in HMRC penalties and interest charges, even if no tax is due or you are entitled to a refund.
Understanding the key deadlines early helps you stay compliant, avoid unnecessary penalties and gives you more time to prepare for any tax payment that may be due.
Key Takeaways
- The 2025–26 tax year runs from 6 April 2025 to 5 April 2026.
- Tell HMRC by 5 October 2026 if you need to file a Self Assessment return and have not previously registered.
- Paper tax returns must normally reach HMRC by 31 October 2026.
- Online tax returns are due by 31 January 2027.
- Any balancing payment due is normally payable by 31 January 2027.
- A second payment on account may be due on 31 July 2027.
- HMRC may charge penalties for both late filing and late payment.
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We prepare and file Self Assessment tax returns for sole traders, landlords, CIS subcontractors and other taxpayers.
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Get a Free QuoteThe 2025–26 Tax Year at a Glance
The 2025–26 tax year runs from 6 April 2025 to 5 April 2026.
If you are self-employed, receive rental income, have untaxed income or have been asked by HMRC to complete a return, you may need to submit a Self Assessment tax return.
The main deadlines fall on a small number of fixed dates, making it worthwhile to prepare your records well in advance.
You can check the official Self Assessment deadlines on GOV.UK at any time to confirm the dates that apply to you.
Key Self Assessment Deadlines
Tell HMRC by 5 October 2026
If you need to complete a Self Assessment tax return for the 2025–26 tax year and have not filed previously, or you were previously registered but did not need to file for 2024–25, you must normally tell HMRC by 5 October 2026.
Registering late does not remove your obligation to pay any tax due by the relevant deadline.
Paper Tax Return Deadline: 31 October 2026
HMRC must normally receive paper tax returns by 31 October 2026.
Most taxpayers choose to file online, which provides a later filing deadline.
PAYE Tax Code Collection Deadline: 30 December 2026
If eligible, some taxpayers may ask HMRC to collect an amount owed through their PAYE tax code.
To be considered, online returns generally need to be submitted by 30 December 2026.
Eligibility conditions apply.
Online Tax Return Deadline: 31 January 2027
The standard deadline for submitting an online Self Assessment tax return for 2025–26 is 31 January 2027.
Filing early provides more time to:
- Check accuracy
- Budget for tax due
- Resolve missing information
- Understand payments on account
Tax Payment Deadline: 31 January 2027
Any balancing payment due for the 2025–26 tax year is normally payable by 31 January 2027.
This is also the date when a first payment on account may become due for some taxpayers.
Second Payment on Account: 31 July 2027
Where payments on account apply, the second instalment is generally due by 31 July 2027.
Payments on account are advance payments towards the following year's tax bill.
Late Filing Penalties
HMRC may charge late-filing penalties even where no tax is due.
Current penalties include:
- £100 initial penalty after the filing deadline.
- Daily penalties of £10 per day after three months, up to a maximum of £900.
- A further penalty after six months of 5% of the tax due or £300, whichever is greater.
- A further penalty after twelve months of 5% of the tax due or £300, whichever is greater.
You can check Self Assessment penalties on GOV.UK for the current rules.
Late Payment Penalties and Interest
Late-payment penalties are separate from late-filing penalties.
HMRC may charge:
- 5% of unpaid tax after 30 days.
- A further 5% after six months.
- A further 5% after twelve months.
Interest may also apply to overdue tax amounts. HMRC interest rates change periodically, so always confirm the current rate before relying on a figure.
You can check current HMRC interest rates on GOV.UK.
Tax Myth Buster
I do not need to file my return if I cannot afford to pay the tax.
Filing and payment are separate obligations. Filing on time may help avoid late-filing penalties, even if tax remains payable.
There is no penalty if I owe no tax.
The initial £100 late-filing penalty can apply even if there is no tax due.
The 2025–26 Self Assessment deadline falls in January 2026.
The 2025–26 tax year ends on 5 April 2026, and the standard online filing deadline is 31 January 2027.
Do You Need to File a Return?
You may need to submit a return if you:
- Are self-employed
- Receive rental income
- Are a CIS subcontractor
- Have untaxed income
- Have capital gains to report
- Receive foreign income
- Have been asked by HMRC to file a return
If you are uncertain, use HMRC guidance to check if you need to send a tax return.
Avoid the January Deadline Rush
Preparing early gives you more time to organise records, budget for tax liabilities and understand whether payments on account may apply.
Accountant Bookkeeping Ltd prepares Self Assessment returns from £150 with no VAT added.
Start Your Self Assessment EnquiryFrequently Asked Questions
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