Back To Basics: Self Assessment – Deadlines and Payment Dates Explained

Who needs to file? When is it due? And what happens if you’re late? If you’re new to Self Assessment or still confused by those dreaded 31st January deadlines, you’re not alone. In this short guide, we’ll break down what you need to know to stay compliant, avoid penalties, and plan ahead.

🧑‍💼 Who Needs to File a Self-Assessment Tax Return?

You must complete a Self-Assessment return if you:

• Are self-employed as a sole trader and earned more than £1,000
• Are a partner in a business partnership
• Are a company director (and earned untaxed income)
• Earn rental income
• Are a UK Resident with Foreign Income (eg. live in Northern Ireland and work in the Republic of Ireland)
• Have income from savings or investments above £10,000
• Receive dividends or other untaxed income

Important: Even if you don’t receive a letter from HMRC, it’s your responsibility to register and file if you meet the criteria.

🗓️ Key Self Assessment Dates

Let’s break it down:

✅ 5 April – End of the Tax Year

• The UK tax year runs from 6 April to 5 April the following year.
• Your 2024/25 return will include income from 6 April 2024 to 5 April 2025.

📝 31 October – Paper Filing Deadline

• If you file your return on paper, it must be with HMRC by 31 October 2025.
• Almost everyone files online nowadays — it’s faster, easier, and buys you more time.

💻 31 January – Online Filing & Payment Deadline

• Your online tax return for the 2024/25 tax year is due by 31 January 2026.
• Any tax owed must also be paid by the same date.

Tip: You can submit your Self-Assessment tax return at any time after the tax year ends — for example, in June — but you don’t need to pay your tax until the deadline on 31st January.

Early filing ≠ early payment.

You can pay in as many or as few payments as you like, as long as the balance is paid in full by 31st January.

💷 31 July – Payments on Account (if applicable)

• If your last tax bill was over £1,000, HMRC may ask you to make advance payments towards your next year’s bill — called Payments on Account.
• These are due in two instalments:
  • 31 January (same day as your main payment)
  • 31 July

Example: If you owed £2,000 for 2023/24, you may be asked to pay £1,000 on 31 Jan 2025 and £1,000 on 31 July 2025 towards your 2024/25 tax.

So, your January payment would be £3,000, and your July payment would be £1,000.

At that point, you would have £2,000 pre-paid towards the following tax year.

❗ What If You’re Late?

📣 Our Advice: File Early, Sleep Easy

Many taxpayers leave it until the last minute, but filing early has real advantages:

• You get more time to budget and plan
• You avoid last-minute stress
• You can spot errors early (or refunds owed!)

If we do your tax return for you, we’ll help you understand:

• What you owe (and why)
• Whether Payments on Account apply
• When and how to pay it

💬 Need Help With Your Self-Assessment?

Whether you’re filing for the first time or you’re sick of doing it alone, we can help. Our team prepares tax returns for self-employed individuals, landlords, company directors, and more — with clear explanations, no jargon, and no last-minute surprises.

👉 Get in touch to have yours filed early and properly.