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By If you’re self-employed, a freelancer, landlord, or earning income outside of PAYE in the UK, you’ll likely need to file a Self-Assessment tax return with HM Revenue & Customs (HMRC). Filing late can result in penalties and interest, so it’s vital to know the deadlines, what documents you need, and how to file correctly.
At TT Accountancy Services (TTAS), we help individuals and businesses in London stay compliant while making tax season stress-free. Below is your complete guide to Self-Assessment tax returns for 2025 and 2026.
Self-Assessment Deadlines for 2025
For the 2023/24 tax year (income earned between 6 April 2023 – 5 April 2024):
- 5 October 2024 – Deadline to register for Self-Assessment (if it’s your first return).
- 31 October 2024 – Deadline for paper tax return submissions.
- 31 January 2025 – Deadline for online filing and payment of tax owed.
Self-Assessment Deadlines for 2026
For the 2024/25 tax year (income earned between 6 April 2024 – 5 April 2025):
- 5 October 2025 – Deadline to register for Self-Assessment (first-time filers).
- 31 October 2025 – Deadline for paper tax return submissions.
- 31 January 2026 – Deadline for online filing and payment of tax owed.
🔗 Official HMRC Self-Assessment deadlines
⚠️ Remember: Missing the deadline triggers an automatic £100 penalty, with further fines and interest for continued delays.
Self-Assessment Checklist: What You’ll Need
To complete your tax return for either year, gather:
- Unique Taxpayer Reference (UTR) number
- National Insurance number
- Income records – invoices, contracts, payslips, rental statements
- Business expenses – receipts, mileage logs, software subscriptions, utilities
- P60, P45, or P11D forms (if employed as well as self-employed)
- Bank interest/dividend statements
- Any foreign income or capital gains
Keeping these organized throughout the year makes filing much easier.
How to File a Self-Assessment Tax Return
- Register with HMRC (if you haven’t before)
🔗 Register for Self-Assessment - Log in online via your Government Gateway account.
- Enter all income details – self-employment, employment, rental, dividends, and other sources.
- Claim allowable expenses to reduce your tax bill.
- Check, review, and submit your return.
- Pay your tax bill by the deadline (31 January of the following year).
🔗 File your Self-Assessment tax return online
Why Work With TT Accountancy Services?
Filing a Self-Assessment tax return can be complex — especially if you have multiple income streams. At TTAS, we:
- Ensure accurate and timely filing
- Maximise tax reliefs and allowances
- Handle HMRC correspondence on your behalf
- Save you time and reduce stress
Contact TT Accountancy Services today for professional Self-Assessment support in London.
The Self-Assessment deadlines for 2025 and 2026 are fast approaching. By preparing early, keeping good records, and working with an expert accountant like TTAS, you can avoid penalties, reduce your tax bill, and focus on growing your business.
Don’t leave it until the last minute — let TTAS take care of your Self-Assessment tax return today.
