Tax Week Calendar 2025/26 | When Are Self Assessments Due?
Another new tax year is upon us, and if you're a business owner, sole trader, or anyone earning income that isn't taxed at source, it's time to check you know when your Self Assessments are due and get those dates in your diary.
Keeping track of HMRC's deadlines isn't just about ticking a box. It's about staying penalty-free, smoothing your cash flow, and planning your finances with confidence. To help, we've pulled together the essential Self Assessment tax dates for 2025/26, with a few extra insights to help you stay ahead.
If you're looking to compare this year's deadlines with last year's, you can also refer to our previous blog on the tax week calendar 2023/24.
The April Transition: From 2024/25 to 2025/26
As one tax year ends and another begins, what action do you need to be taking? Here's a look at what this changeover period means for your business:
5 April 2025: End of the 2024/25 Tax Year
This date is important, as it is your final opportunity to make use of any tax reliefs or allowances for the 2024/25 year. Be sure to review all your income, expenses, and any potential claims, remembering to include things such as pension contributions, charitable donations, or allowable business expenses, which will help optimise your tax contributions.
6 April 2025: Start of the 2025/26 Tax Year
As a fresh financial year begins, it's a good idea to evaluate your record-keeping systems, especially if you're preparing for the upcoming changes under Making Tax Digital (more on that below). Remember also to check your new tax codes and allowances so you can adjust your financial plan accordingly from the outset.
When Are Self Assessments Due? Key Deadlines to Know
While the new tax year starts in April, most Self Assessment deadlines fall later in the year, with one important exception relating to the previous tax year. Here are the key Self Assessment dates that you need to mark on your calendar:
30 April 2025: Final Deadline for Overdue 2023/24 Tax Returns
If you still haven't filed your tax return for the 2023/24 tax year, this date is your last chance before daily penalties start to apply. From 1 May, HMRC may begin charging £10 per day (for up to 90 days), so it's vital to act now to avoid escalating fines.
31 July 2025: Second Payment on Account for 2024/25 Tax Year
If you make payments on account, this is when your second instalment for the 2024/25 tax year is due. Payments on account are based on last year's bill, helping you spread the cost by making two instalments and avoiding a big lump sum in January.
5 October 2025: Register for Self Assessment
If you are newly self-employed or have received untaxed income in 2024/25, you must register with HMRC by this date to submit a return. Registering late could mean delays in receiving your Unique Taxpayer Reference (UTR) and, ultimately, fines.
31 October 2025: Paper Tax Return Deadline
If you're filing your return on paper, this is your cut-off. Most people now file online, which gives you until January and provides instant submission confirmation.
30 December 2025: PAYE Option for Tax Collection
If you're employed and owe less than £3,000 in tax, you may be able to have the tax collected via your PAYE code over the following year if you submit your online return by this date and meet HMRC's specifications. It's a great way to spread the cost, especially helpful if you're balancing self-employed income with a salaried job.
31 January 2026: Final Filing & Payment Deadline
This date is the significant one. Check you have completed the following key actions by this point:
- Filed your Self Assessment tax return for 2024/25.
- Paid any tax owed (your "balancing payment") from 2024/25.
- Made your first payment on account for 2025/26 (if applicable).
If you miss this deadline, you'll be hit with a £100 penalty plus further interest and charges the longer it goes unpaid.
31 July 2026: Second Payment on Account 2025/26 Tax Year
It's time for your second payment on account (advance tax payment) again, this time for the 2025/26 tax year. Remember, HMRC uses these advance payments to spread your tax bill across the year, based on your previous return, so it's worth checking whether your earnings have changed as you may be able to make a claim to reduce it.
What's New for 2025/26?
Making Tax Digital (MTD) for Income Tax Is Coming
From 6 April 2026, if you earn over £50,000 from self-employment or property, you will need to follow MTD rules, i.e., keeping digital records and submitting quarterly updates to HMRC. If you earn over £30,000, this update will apply to you from 2027.
Personal Allowance Frozen
The personal allowance (the amount you can earn tax-free) remains at £12,570. With inflation pushing incomes higher, more people may find themselves liable for income tax, so it's worth reviewing your income and tax code early in the year.
Closing Advice
Tax deadlines don't have to be a source of stress. By staying on top of the calendar and getting organised early, you can avoid penalties, plan your payments, and make the most of any tax-saving opportunities.
At Keith Graham, we work closely with businesses and individuals to take the pressure off at tax time. Our highly experienced Chartered Accountants offer comprehensive Self Assessment services and guidance to help make Self Assessment simple.
Please get in touch today to find out how we can help.