Self Assessment Tax Calendar 2025/26: Key Dates You Need to Know
Ryan Scott • 20 April 2025
Key Dates to Stay Ahead for 2025/26
The new tax year is here again! If you're a business owner, sole trader, or anyone earning income that isn’t taxed at source, it’s time to make sure you’re up to date on your Self Assessment deadlines. Add these important dates to your diary now and stay ahead of the curve.
Staying on top of HMRC’s deadlines isn’t just good admin—it helps you avoid penalties, manage your cash flow, and plan your finances more effectively. To make it easy, we’ve laid out all the key Self Assessment dates for 2025/26, plus some practical insights to help you stay in control.
Need to compare with last year’s calendar? You can check out our blog covering the 2023/24 tax week dates for a full comparison.
April Tax Year Transition: From 2024/25 to 2025/26
As one tax year wraps up and another begins, here’s what you need to know:
5 April 2025 – End of the 2024/25 Tax Year
This is your final chance to use any tax reliefs or allowances for the 2024/25 year. Make sure you’ve reviewed your income, expenses, and any potential claims, such as pension contributions, charitable donations, or business expenses to help minimise your tax liability.
6 April 2025 – Start of the 2025/26 Tax Year
A new financial year is a great opportunity to review your bookkeeping processes, especially with Making Tax Digital changes on the horizon. Double-check your new tax codes and allowances and update your financial plan accordingly.
Self Assessment Deadlines: What to Watch For
Although the tax year starts in April, most Self Assessment deadlines come later—apart from one key date for late 2023/24 submissions. Here are the essential ones to note:
30 April 2025 – Final Deadline for 2023/24 Late Returns
Haven’t filed your 2023/24 tax return yet? This is your last chance before daily penalties of £10 (up to 90 days) kick in from 1 May. Don’t delay!
31 July 2025 – Second Payment on Account for 2024/25
If you make payments on account, this is when your second instalment for the 2024/25 tax year is due. These payments help spread your tax bill over the year to avoid a hefty lump sum in January.
5 October 2025 – Deadline to Register for Self Assessment
Newly self-employed or earned untaxed income in 2024/25? You must register with HMRC by this date to file your return. Late registration can lead to delays and potential penalties.
31 October 2025 – Paper Tax Return Deadline
Still filing on paper? This is your final date to submit. Online filing gives you until January and includes instant confirmation.
30 December 2025 – PAYE Tax Collection Option
If you're employed and owe less than £3,000 in tax, submitting your online return by this date may let HMRC collect what you owe via your tax code—spreading the cost across the year.
31 January 2026 – Final Filing & Payment Deadline
This is the big one! By now, you must have:
• Submitted your 2024/25 Self Assessment tax return
• Paid any tax owed for 2024/25
• Made your first payment on account for 2025/26 (if applicable)
Missing this deadline triggers an automatic £100 fine and further penalties the longer it goes unpaid.
31 July 2026 – Second Payment on Account for 2025/26
Time for your second advance payment for the 2025/26 tax year. Payments are based on your previous return, so if your income has dropped, you might be able to reduce this—worth checking in with your accountant.
What’s New in 2025/26?
Making Tax Digital (MTD) Is Almost Here
Starting 6 April 2026, if you earn over £50,000 from self-employment or property, you’ll need to follow MTD rules—keeping digital records and sending HMRC quarterly updates. Those earning over £30,000 will be included from 2027.
Personal Allowance Still Frozen
The personal allowance remains at £12,570. With inflation, more people may be pushed into tax brackets, so it’s worth reviewing your income and tax code early in the year.
Whether you are a Sole Trader, Partner, or Director, SBX have custom self-assessment services tailored to you.
For further advice or information on Self Assessment deadlines and managing your taxes,
Contact us.
If you’re running your business through a limited company - or thinking about incorporating - understanding how dividends work can be a game-changer when it comes to your take-home pay . At SBX Accountants , we specialise in helping business owners like you get the most from your earnings while staying fully HMRC-compliant. One of the most effective ways to do that? Dividends. Dividends are a smart, tax-efficient way to extract profits from your company - but it’s essential to know how they work and how to use them wisely. In this guide, we’ll break it all down and show you how SBX can support you in figuring out the best structure for your business. What Are Dividends (And Why Do They Matter)? Dividends are payments made to shareholders - typically from a company’s retained profits. If you’re both a director and shareholder in your limited company, you can pay yourself dividends in addition to a salary. Why does this matter? Because dividends are taxed at lower rates than regular income, and they’re not subject to National Insurance Contributions (NICs). That means more money in your pocket, and less to the taxman. At SBX, we help you build a smart remuneration strategy that uses dividends to your advantage - without overstepping any legal or compliance boundaries.
If you're running a business as a sole trader, it’s your responsibility to make sure you’re paying the correct amount of Income Tax and National Insurance. To do this, most sole traders need to register for Self Assessment with HMRC – but the rules can vary depending on how much you earn and whether you’re also employed. When Does a Sole Trader Need to Register for Self Assessment? As a self-employed individual , you must register for Self Assessment so you can file an annual tax return. This allows HMRC to calculate what you owe in tax and National Insurance contributions. The general rule is: 🔹 If you earn more than £1,000 from self-employment in a single tax year (6 April to 5 April), you must register for Self Assessment . This applies whether your business is full-time, part-time, or even a casual side hustle
Sole Trader vs. Limited Company: Key Differences Explained
