Self Assessment Tax Return UK – What Tax Return Is Due Jan 2026 (31 January Deadline)
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Self Assessment January 2026: Complete Guide to Filing & Deadlines
Filing your Self Assessment tax return in January 2026 is one of the most important financial responsibilities for UK taxpayers — including sole traders, freelancers, landlords and company directors. If you miss the tax return deadline UK – 31 January 2026, HMRC will charge automatic penalties and interest no matter your income.
In this Self Assessment guide for January 2026, we’ll explain:
- What tax return is due Jan 2026
- Which tax year you are filing
- Self Assessment deadlines UK
- Penalties for late filing or payment
- How to complete and submit your online tax return
- New Self Assessment rules and changes
What Tax Return Is Due Jan 2026? | Which Tax Year It Covers
The Self Assessment tax return due on 31 January 2026 covers income for the 2024/25 tax year — that is from 6 April 2024 to 5 April 2025.
This means if you earned untaxed income (self-employment profits, rental income, dividends, foreign income, etc.) during that period, you must report it to HMRC and pay any tax owed by the tax return deadline 31 January 2026.
Key Self Assessment Deadlines January 2026
Here are the crucial Self Assessment deadlines UK to remember:
| Deadline | Task |
|---|---|
| 5 October 2025 | Last day to register for Self Assessment if you’re new |
| 31 October 2025 | Paper tax return due |
| 31 January 2026 | Online tax return and tax payment due (Self Assessment January 2026 deadline) |
| 31 July 2026 | Second payment-on-account if applicable |
Online filing and the tax balance must both be completed by 31 January 2026 at 11:59 pm to avoid penalties.
Who Must Submit a Self Assessment Tax Return
You will usually need to submit a self-assessment if, in the tax year:
- You were self-employed or a sole trader
- You received rental income
- You are a company director
- You earned significant dividends or foreign income
- Your untaxed income exceeded HMRC thresholds
How to File Your Self Assessment Tax Return in January 2026
Step 1: Register with HMRC
If it’s your first return, you must register by 5 October 2025 to receive your Unique Taxpayer Reference (UTR).
Step 2: Gather Documents
Collect:
- Income records
- Expense receipts
- P60/P45
- Rental income summaries
- Bank and dividend statements
This ensures accurate reporting and fewer mistakes.
Step 3: Complete and Submit Online
Log into HMRC’s online service, complete the return for the what year tax return is due now (2024/25), and submit before 31 January 2026.
Step 4: Pay Your Tax
Tax owed must also be paid by 31 January 2026. You can pay by bank transfer, debit card or arrange a Time to Pay plan if needed.
What Happens If You Miss the January 2026 Tax Return Deadline
Missing the tax return deadline UK — 31 January 2026 results in automatic penalties from HMRC:
- £100 immediate late filing penalty
- £10 per day after 3 months (up to £900)
- 5% of tax due after 6 and 12 months
- Interest on late payment of tax owed
Even if you can’t pay your tax bill now, you should still file on time and arrange a payment plan.
New Self Assessment Rules & Changes from April 2026
Starting 6 April 2026, Making Tax Digital (MTD) for Income Tax Self Assessment begins to roll out. Eligible taxpayers (especially those earning above certain thresholds) will have to:
- Use compatible digital software
- Submit quarterly income and expense updates
- Finalise the annual Self Assessment return digitally
This represents a shift from the traditional annual return system and may affect how you prepare next year.
Tips to Reduce Your Tax Bill Before 31 January 2026
- Claim all allowable business expenses
- Maximize pension contributions
- Use personal and trading allowances
- Work with an Chartered Accountant to find tax-efficient strategies
FAQ: Self Assessment January 2026
Q: What tax year is due in Jan 2026?
The tax return due on 31 January 2026 covers income earned in the 2024/25 tax year (6 April 2024 to 5 April 2025).
Which tax year is due in January 2026?
You must file your 2024/25 Self Assessment tax return by the UK deadline of 31 January 2026.
What happens if I miss the Self Assessment deadline?
HMRC issues an immediate £100 penalty, followed by daily fines and interest on unpaid tax.
Can I submit my tax return if I can’t pay the tax?
Yes — you should still file on time and apply for an HMRC Time to Pay arrangement.
Are there new Self Assessment rules in 2026?
Yes — Making Tax Digital for Income Tax begins rolling out from April 2026, requiring quarterly reporting for some taxpayers.
Conclusion: Don’t Delay Your Self Assessment Tax Return
The Self Assessment tax return January 2026 deadline is fixed. Filing early reduces stress, avoids penalties, and can help you plan cash flow effectively. Align your filing with the what tax return is due Jan 2026 and make sure you understand which tax year is due in January 2026.
If you want support filing your Self Assessment or navigating new self assessment rules, working with a qualified accountant is a wise choice.
