# UK Self Assessment deadlines and late filing penalties for 2025/26 A comprehensive guide to the UK 2025/26 Self Assessment deadlines, detailing paper and online filing dates, HMRC late penalties, interest charges, and the appeals process. **Published:** 2026-07-03 **Updated:** 2026-07-03 **Source:** https://aztajournal.com/gb/self-assessment-deadlines-penalties --- > This guide outlines the critical deadlines and penalty frameworks for the UK 2025/26 Self Assessment tax year. Learn the key dates for paper and online submissions, how HM Revenue and Customs calculates late fees, and how to appeal a penalty. The 2025/26 Self Assessment deadlines require paper tax returns to be submitted by 31 October 2026, while online returns and final tax payments must be completed by 31 January 2027. Missing these statutory dates triggers automatic penalties and interest charges from HM Revenue and Customs (HMRC), even if you do not owe any tax. If your tax return is delayed, the financial penalties scale progressively based on how late the submission remains. ## Key Takeaways: 2025/26 Self Assessment - **Paper Filing Deadline**: Must be submitted to HMRC by 31 October 2026. - **Online Filing Deadline**: Must be submitted to HMRC by 31 January 2027. - **Tax Payment Deadline**: The final payment for tax owed is due by 31 January 2027. - **PAYE Coding Deadline**: File online by 30 December 2026 to have tax debts under £3,000 collected through your tax code. - **Late Filing Penalty**: An automatic £100 fine applies immediately the day after the deadline passes. ## When is the 2025/26 Self Assessment deadline? The deadlines for the 2025/26 Self Assessment tax year require filing by 31 October 2026 for paper returns and by 31 January 2027 for online returns. According to official GOV.UK rules, taxpayers must also complete their final payments by 31 January 2027. If you prefer to have your outstanding tax collected automatically through your PAYE salary tax code, you must submit your online return by the earlier deadline of 30 December 2026. | Submission Method / Action | HMRC Deadline Date | | --- | --- | | Paper Tax Return | 31 October 2026 | | Online Tax Return (PAYE Code Collection Option) | 30 December 2026 | | Online Tax Return (Standard) | 31 January 2027 | | Payment of Tax Owed | 31 January 2027 | ## How much is the penalty for late Self Assessment? Late filing penalties start with an automatic £100 charge and can accumulate to a minimum of £1,600 if the return is delayed by 12 months. Under Schedule 55 of the Finance Act 2009, HMRC applies fixed and percentage-based penalties at statutory milestones. If a return is delayed for a full year, the accumulated penalties can reach thousands of pounds, especially if HMRC determines that information was deliberately withheld. 1. **Day 1 late**: An automatic £100 penalty is issued immediately the day after the filing deadline. 2. **3 months late**: Daily penalties of £10 per day accumulate for up to 90 days, adding up to a maximum of £900. 3. **6 months late**: A penalty of 5% of the tax owed or £300 is charged, depending on which figure is greater. 4. **12 months late**: An additional penalty of 5% of the tax owed or £300 is applied, depending on which figure is greater. ## What are the penalties for late tax payment? Late tax payments trigger percentage-based surcharges starting at 30 days overdue, alongside daily interest calculations until the balance is fully cleared. HMRC assesses late payment charges entirely separately from late filing penalties. These percentage-based penalties apply only to the unpaid tax balance remaining at each specific chronological marker. - **30 days late**: A penalty of 5% of the tax remaining unpaid at this specific date is applied. - **6 months late**: An additional penalty of 5% of the unpaid tax balance is added to the account. - **12 months late**: A final penalty of 5% of the outstanding unpaid tax balance is charged. - **Daily Interest**: HMRC charges interest on all unpaid amounts, calculated at 4 percentage points above the Bank of England base rate. ## Can you appeal an HMRC late filing penalty? Yes, you can appeal an HMRC late filing penalty if you have a valid, documentable reasonable excuse for missing the submission deadline. Taxpayers must typically submit their late return before lodging an official appeal. HMRC will evaluate the individual circumstances of the delay to determine if the penalty can be cancelled under their statutory guidelines. - **Reasonable Excuses**: HMRC accepts serious unpredictable events such as a close bereavement, severe illness, or unexpected technical failures of HMRC online services. - **Filing First**: You must file your outstanding tax return with HMRC before you can formalise an appeal against the penalty. - **Time Limits**: Appeals should be submitted to HMRC within 30 days of the date printed on the penalty notice. ### What if I cannot afford to pay my tax bill? You can establish an official Time to Pay instalment agreement with HMRC to spread the cost of your tax debt over multiple monthly payments. 1. **Check Your Eligibility**: Ensure your total tax debt is £30,000 or less, and that you are within 60 days of the initial payment deadline. 2. **Access the Setup Tool**: Log into your HMRC online tax account to access the self-service Time to Pay portal. 3. **Choose Your Terms**: Set up a direct debit schedule to split your tax liability into manageable monthly payments. 4. **Pay Remaining Interest**: Acknowledge that HMRC will still calculate daily interest on the unpaid balance for the duration of the plan. ### What is the late filing penalty if I owe no tax? The automatic £100 penalty still applies on day one even if you owe no tax to HMRC, or if your tax liability has already been fully paid. ### Can HMRC collect my tax bill through my PAYE tax code? Yes, HMRC can collect tax balances under £3,000 through your PAYE tax code, provided you submit your completed online return by 30 December 2026. ### What is a reasonable excuse for late tax filing? A reasonable excuse is an unexpected or severe event that stopped you from filing on time, such as a serious illness, recent bereavement, or HMRC service failure. ### How do I appeal a Self Assessment penalty? You must first file your late tax return, and then submit a formal appeal online or by post within 30 days of receiving the penalty notice.