Self Assessment Deadline 31 January 2027: Your Checklist
Updated: 4 hours ago
The deadline for filing your 2025 to 2026 Self Assessment tax return online is 11:59pm on Sunday 31 January 2027. It's also the day any tax you owe has to be paid. Every year, thousands of people leave it until the last week and end up stressed, short of paperwork or paying a penalty. This checklist will help you get it done in good time.
Key Self Assessment dates for 2025 to 2026
5 October 2026: deadline to register for Self Assessment if you're filing for the first time (now passed. If you've missed it, register as soon as possible)
31 October 2026: deadline for paper returns (now passed)
30 December 2026: file online by this date if you want tax under £3,000 collected through your PAYE tax code
31 January 2027: online filing deadline, and payment of any balance owed for 2025 to 2026 plus your first payment on account for 2026 to 2027
31 July 2027: second payment on account for 2026 to 2027
Your Self Assessment checklist
1. Make sure you can log in
Check now that you can get into your HMRC online account and that you have your Unique Taxpayer Reference (UTR). Resetting passwords or waiting for an activation code by post can take longer than you'd expect, so don't leave this until January.
2. Gather your income records
Self-employed income: sales invoices, takings records and bank statements for the year to 5 April 2026 (or your accounting year)
Rental income: rent received, letting agent statements and details of any properties bought or sold
Employment income: your P60 and any P11D for benefits such as a company car
Other income: bank and building society interest, dividends, pensions and any partnership share
3. Gather your expenses
Claiming every allowable expense is one of the simplest ways to make sure you don't pay more tax than you need to. Pull together receipts and records for things like materials and stock, travel and vehicle costs, phone and internet, insurance, professional fees, use of home as an office and, for landlords, repairs, letting fees and mortgage interest (which gets a 20% tax credit, not a full deduction).
4. Don't forget the extras
Pension contributions and Gift Aid donations, which can reduce your tax if you're a higher-rate taxpayer
Student loan repayments
Child Benefit, if you or your partner earn over £60,000 (the High Income Child Benefit Charge)
Capital gains from selling property, shares or other assets
5. Plan for payments on account
If your tax bill is more than £1,000 and less than 80% of your tax was taken at source, HMRC will usually ask you to pay towards next year's bill in advance. That's half in January and half in July. This catches many people out in their second year of self-employment, when January's bill can suddenly look much bigger. If your income has dropped, you may be able to apply to reduce them.
6. File early, pay on time
Filing early doesn't mean paying early. You still have until 31 January to pay. But it does mean you know exactly what you owe and have time to budget for it. If you can't pay in full, HMRC may agree a Time to Pay arrangement, but you need to contact them.
What happens if you miss the deadline?
An immediate £100 penalty for a late return, even if you owe no tax
After 3 months, £10 a day for up to 90 days (up to £900)
After 6 months, a further 5% of the tax due or £300, whichever is greater, and the same again after 12 months
Late payment penalties of 5% of the unpaid tax at 30 days, 6 months and 12 months, plus interest
A return filed a few months late could easily cost you over £1,000 in penalties, even before interest.
Making Tax Digital is coming
If you're a sole trader or landlord with income over £30,000, your 2025 to 2026 return is also the one HMRC will use to decide whether you need to join Making Tax Digital for Income Tax from April 2027. It's worth getting it right. Read our Making Tax Digital guide to find out more.
Let us take care of it
We've been preparing Self Assessment tax returns for sole traders, landlords, partners and company directors in Sheffield since 1996. Send us your paperwork and we'll prepare your return, check you're claiming everything you're entitled to and file it with HMRC, so you're not worrying about it at the end of January. Find out more about our Self Assessment service.
Don't leave it until January. Book a free consultation or call us on 0114 274 7759.
This article is general guidance based on HMRC information available in November 2026. Please get advice on your own circumstances.
