Self Assessment Tax Return Filing Deadline 2026 – Everything You Must Know Before 31 January

What is the Self Assessment Tax Return Filing Deadline for 2026?

There are two deadlines to remember. The paper filing deadline is 31 October 2025. The online filing deadline is 31 January 2026. Most people file online because it takes less time and fewer errors are made.

You need to pay any tax due by 31 January 2026, so filing early gives you more time to prepare.

Key Self Assessment Dates for 2024–25

Here are the key dates you should keep an eye on:

• 5 April 2025: Tax year ends.
• 31 October 2025: Deadline for paper returns for the 24-25 tax year expires.
• 31 January 2026: Deadline for online filing and payment of any tax owed for 24-25.

These dates are the same each year.

Who Needs to File a Self Assessment Tax Return?

You must file a return if any of the following apply:

• You are self employed.
• You earn more than £1,000 from self employment.
• You are a partner in a business partnership.
• You earn untaxed income such as rental income, dividends or foreign income.
• You earn more than £100,000.
• You need to claim certain tax reliefs.
• HMRC has asked you to file a return by writing to you.

If you are unsure, check with an accountant to avoid late-filing penalties later.

How to File Your Self Assessment Tax Return Before 31 January 2026

Register with HMRC if this is your first time filling in a tax return. When you register, HMRC will write back to you with a notice to file, and importantly- will provide you with a Unique Taxpayer Number (a ‘UTR’).

Your UTR is a key piece of date. You will only receive one UTR in your lifetime, so if you lose this reference number, you’ll need to contact HMRC and persuade them to send out another copy of this number for you. This can be a time consuming and frustrating process. Keep your UTR stored safely!

When you have a UTR, gather your income records, expenses and documents together. Log in to your HMRC online account and follow the steps to enter your figures. Check everything carefully before submitting. Once you file, you will see how much tax you owe.

For a detailed guide on filing your Self Assessment Tax Return online, visit our step-by-step guide

Key Steps if You’re Filing Close to the Deadline

If you are close to the deadline, here is a more complete checklist to help you stay organised:

• Make sure you can log in to your HMRC account.
• Check you have your Unique Taxpayer Reference and National Insurance number.
• Gather your income records, expense receipts and bank statements.
• Check employment documents such as P60s or P45s.
• Review rental income records or dividend statements if you have them.
• Double check your bank interest statements.
• Make sure your bookkeeping is up to date if you are self employed.
• File your return as soon as possible to avoid penalties.
• Pay your tax bill early so the funds clear in good time.
• Keep a copy of your submission receipt for your records.

What Are the Self Assessment Penalties for Missing the Deadline?

Penalties can get expensive. Here are the current rules:

• One day late: £100 fixed penalty.
• Three months late: Daily penalties of £10 per day for up to 90 days.
• Six months late: HMRC may charge 5 percent of the tax owed.
• Twelve months late: Another 5 percent added.

Interest is charged on unpaid tax from the day after the deadline.

What If I’m Late? How to Mitigate Penalties and Next Steps

If you miss the deadline, file your return as soon as possible to limit penalties. If you have a genuine reason, such as illness or bereavement, you can appeal. HMRC will ask for evidence. 

If you cannot pay in full, consider a Time to Pay arrangement which lets you spread the cost monthly.

Can I Still File a Paper Tax Return After the HMRC Deadline?

The paper filing deadline is 31 October 2025. Returns after this date must be filed online. HMRC only accepts paper returns after the deadline in exceptional circumstances. This usually requires proof that online filing was not possible. Most taxpayers will need to file online once the October deadline has passed.

Can an Accountant File My Self Assessment for Me?

Yes. An accountant can file the return on your behalf, check the figures and make sure everything is accurate. This helps avoid mistakes and saves time.

A key advantage of having an accountant file your Self-Assessment tax return is that they will advise over whether your return is accurate. They can also provide advice over which specific allowances are claimable and what expenses you are allowed to deduct from your income. Having a professional accountant file your tax return can lead to tax savings and also can provide significant peace of mind.

How Can I Pay My Self Assessment Tax Bill?

You can pay by bank transfer, direct debit, online banking, card payment or bank giro. Pay early so the funds clear on time. If you cannot pay in full, use HMRC’s Time to Pay service.

Most of our clients pay HMRC by direct bank transfer. As long as your payment is within the Faster Payments limits, your funds should land with HMRC and be cleared the same day.

Is There a Self Assessment Checklist I Can Use to File on Time?

Here is a simple checklist of all potential item you need to consider before you file your self-assessment tax return. Pull your paperwork together before filing your tax return so you have all the information ready and on hand.

• P60 or P45 forms if you were employed during the year.
• P11D showing any benefits in kind, such as company cars or medical insurance.
• Income records if you are self employed, including sales invoices and bookkeeping reports.
• Expense receipts for allowable business costs.
• Rental income statements and property expense records if you receive rental income.
• Share transaction records if you bought or sold shares, including dates, purchase cost and sale proceeds.
• Capital gains records for sale of property, shares or other assets.
• Child Benefit details if you or your partner receive Child Benefit and your income is over £60,000.
• Student loan statements if you are repaying a student loan.
• Gift Aid donation records for any charitable donations.
• Pension contribution statements for personal or workplace pensions.
• Bank interest statements for any savings income.
• Dividend vouchers if you received dividend payments.
• Foreign income records if you receive income from outside the UK.
• Partnership statements if you are part of a business partnership.
• Any correspondence from HMRC relating to your tax code or adjustments during the year.

Where Can I Get More Guidance From HMRC?

HMRC provides online tools, guides and video support. These can be helpful, but they can also feel overwhelming. If you want tailored advice, it is best to speak with an accountant.

How We Can Help – Chartered Accountant for Self Assessment

We help individuals and small business owners file their Self Assessment quickly and accurately. We handle the process, review your figures and explain everything clearly. Most importantly, we advise you what you can claim in the way of expense and reliefs. If you need help, book a call with our team and we will guide you through each step.

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