The UK tax year running from 6 April 2025 to 5 April 2026 might feel a long way off, but the key deadlines arrive faster than most people expect. Whether you’re a sole trader, landlord, company director, or anyone else who needs to complete a Self Assessment tax return, getting ahead of the dates can save you stress, penalties, and last‑minute scrambles.
This guide breaks down the essential deadlines for filing and paying your 2025–26 tax return—and explains what each one actually means.
📅 Key Filing Deadlines
Paper Tax Returns: 31 October 2026
If you prefer to file a paper return, HMRC must receive it by this date. Not “posted by”—received. With postal delays becoming more common, most people now choose to file online instead.
Online Tax Returns: 31 January 2027
This is the big one. The majority of taxpayers file online, and the final deadline is midnight on 31 January 2027.
Miss it, and HMRC will issue an automatic £100 penalty—even if you don’t owe any tax.
Want to Pay Through Your PAYE Tax Code? Deadline: 30 December 2026
If you owe less than £3,000 and have PAYE income (e.g., employment or pension), you can ask HMRC to collect the tax through your tax code. To do this, your online return must be submitted by 30 December 2026.
💷 Payment Deadlines
Filing is only half the story—payments matter just as much.
Balancing Payment for 2025–26: 31 January 2027
This is when you pay any tax still owed for the year.
First Payment on Account for 2026–27: 31 January 2027
If you’re required to make payments on account, the first instalment for the next tax year is due on the same day as your balancing payment.
Second Payment on Account for 2025–26: 31 July 2026
This one catches many people off guard. If you make payments on account, your second instalment is due before the tax year even ends.
🧾 Registering for Self Assessment for the First Time?
If you’ve never filed a Self Assessment return before but need to for 2025–26, you must register with HMRC by 5 October 2026.
This applies to new sole traders, landlords, and anyone with untaxed income.
🧠 Why These Deadlines Matter
HMRC penalties escalate quickly:
- £100 immediately for missing the filing deadline
- Daily penalties after 3 months
- Additional penalties at 6 and 12 months
- Interest charged on late payments
Staying ahead of the dates isn’t just good practice—it protects your cash flow and keeps your business running smoothly.
✔️ Final Thoughts
The Self Assessment system can feel overwhelming, especially for new business owners or those juggling multiple income streams. But with the right preparation—and a clear understanding of the deadlines—you can avoid penalties and keep your finances on track.