Never miss a self-assessment deadline again. Complete timeline, penalty structures, and expert tips for stress-free submission.
Register for Self Assessment if you're filing for the first time
Submit paper tax returns for the 2025/26 tax year
File online if you want HMRC to collect tax through PAYE code
Final deadline for online tax returns and payment for 2025/26
Understanding the costs of missing deadlines
£100 fixed penalty
£10 per day (max 90 days = £900)
£300 or 5% of tax due (whichever is greater)
£300 or 5% of tax due (whichever is greater)
HMRC charges interest on late payment of tax from the payment deadline (31 January) until the date you pay. The current interest rate is updated regularly on the HMRC website.
Don't wait until January. Begin gathering your documents and information in November or December to avoid last-minute stress.
Maintain digital records throughout the year using accounting software or spreadsheets to make the process smoother.
Set up calendar reminders for key dates, especially 30 days before each deadline to give yourself buffer time.
If your tax affairs are complex, hiring an accountant can save time, reduce errors, and potentially save you money.
Set aside money throughout the year for your tax bill to avoid financial strain when January arrives.
Review your return carefully before submission. Common errors include missing income sources or incorrect calculations.