When is the Self Assessment Tax Deadline?

PHS Team

22 Nov, 2025

If you’re not sure about when is the Self Assessment Tax Deadline, the key date to remember is 31 January. This is the online filing deadline for the 2024/25 tax year.

If you plan to submit a paper return, the deadline comes earlier on 31 October. Most people now file online because it’s quicker and gives them more time to get everything ready.

These are the key self-assessment tax dates, and we’ll be explaining each one in detail as you go through the blog. Filing early gives you more time to get everything sorted and helps you avoid any last-minute stress.

When is the Self Assessment Tax Deadline?

The self-assessment deadline is the date by which anyone is required to file a tax return. For most taxpayers, the deadline for submitting your return online is 31 January following the end of the tax year on 5 April. For example, for the tax year ending 5 April 2025, the online return must be submitted by 31 January 2026.

If you prefer to submit a paper return, the self-assessment tax return deadline is earlier, on 31 October of the same year. So, for the 2024/25 tax year, a paper return must be filed by 31 October 2025.

It’s also important to remember that any tax owed must be paid by 31 January. Missing these deadlines can result in penalties and interest charges.

Self Assessment Tax Dates

Here are the important self-assessment tax dates for the tax year running from April 6, 2025, to April 5, 2026:

Who Needs to Register?

If you earned untaxed income (above the allowance), you must register for self-assessment by 5 October following your first tax year. This deadline applies if you became self-employed or started earning rental or side income after April.?

Registering late can get you a fine, so make sure to set up your HMRC account early and keep your Unique Taxpayer Reference safe. Self-assessment registration deadline reminders can help new taxpayers avoid missing key dates.?

Self Assessment Tax Return Login

To get started with your self-assessment tax return, log in to your online tax account. If it’s your first time filing, make sure your account is set up and ready to use so you can complete your return on time.

• Access your account - View your tax records and previous submissions.
• Submit your return online - Complete and send your self-assessment form online.
• Track key dates - Keep an eye on all important self-assessment tax dates to avoid missing deadlines.
• Review your payment obligations - Check when self assessment payment is due and plan accordingly.
• Update personal details - Make sure your account has current contact and income information.

When is self-assessment payment due?

Paying your taxes on time is just as important as submitting your return. Here are the key dates to keep in mind:

• 31 January - Deadline for submitting your online return and paying any tax owed for the previous tax year.
• 31 July - Due date for the second instalment of payments on account, if applicable.
• Avoid penalties - Paying after these dates can result in interest and fines, so it’s important to plan.
• Plan your funds - Make sure you have enough set aside to cover both your tax bill and any payments on account.

What Happens If You Miss a Self-Assessment Deadline

Missing a self-assessment deadline can lead to penalties and extra charges. Here’s what you need to know:

• £100 automatic penalty - If you miss the online filing deadline on 31 January, you’ll be charged £100, even if you don’t owe any tax.
• Additional penalties - Fines increase if your return remains late after 3, 6, and 12 months.
• Interest on unpaid tax - Any tax not paid by the deadline will attract interest and additional charges.
• Avoid extra costs - Knowing when is the Self Assessment Tax Deadline helps you stay on track and prevent unnecessary fees.

Special Cases That Can Affect Deadlines

Some taxpayers have slightly different deadlines depending on their situation. Key points to note:

• Paper returns - If you submit a paper return instead of online, the self-assessment tax return deadline is 31 October.
• Late registration - Registering after the usual deadline can change your filing timeline.
• Other circumstances - Certain situations, like newly self-employed status or changes in income, may affect your self-assessment tax dates.

Tips to Stay Organised and Meet Deadlines

Being prepared early makes it much easier to meet your deadlines. Here’s how:

• Mark key dates - Registration by 5 October, paper return by 31 October (if needed), online return and payment by 31 January.
• Collect records early - Gather income, expenses, and receipts in advance so you’re ready when When is the Self Assessment Tax Deadline arrives.
• Use online filing - It’s faster, flexible, and gives more time than paper submissions.
• Plan your payments - Set aside funds well before when is self assessment payment due to avoid last-minute stress.
• Stay informed - Keep up with any changes in filing requirements that could affect whether you need to submit a return.

Need Help With Self Assessment?

Choosing the right accountant makes the whole process easier. PHS Associates helps small business owners, freelancers, and landlords keep up with all self-assessment tax return deadlines and rules. Expert tax guidance means fewer worries about missing deadlines and more time for your business.

Call 0208 8611685 or email info@phs-uk.co.uk if you need specialist help with your self-assessment tax return or registration.

Frequently Asked Questions