Deadlines & reminders
Every key date for the 2025/26 tax year — with live countdowns and a one-click calendar download so you never miss a filing or payment deadline.
Next deadline
Register for Self Assessment
5 October 2026
All deadlines
First payment on account
31 January 2026
First instalment of your 2025/26 tax bill — 50% of the previous year's liability.
Register for Self Assessment
5 October 2026
Deadline to register with HMRC if this is your first year of self-employment or new untaxed income.
Paper Self Assessment return
31 October 2026
Deadline to file your 2025/26 tax return on paper if you prefer not to file online.
Online Self Assessment filing deadline
31 January 2027
File your 2025/26 return online and pay any tax owed by midnight on 31 January 2027.
Second payment on account
31 January 2027
Second instalment of your 2025/26 estimated tax bill — also due 31 January alongside your return.
First payment on account (2026/27)
31 January 2027
First instalment towards your 2026/27 bill — also due 31 January alongside your filing.
Second payment on account (2026/27)
31 July 2027
Second instalment toward your 2026/27 tax bill.
What happens if you miss a deadline?
1 day late — filing
£100An automatic £100 penalty applies the day after the 31 January deadline, even if you have no tax to pay.
3 months late — filing
£10/dayDaily penalties of £10 per day for up to 90 days (up to £900 on top of the initial £100).
6 months late — filing
5% or £300A further penalty of 5% of the tax due or £300, whichever is greater.
Late payment
Interest + 5%Interest accrues from the due date. Surcharges of 5% apply at 30 days, 6 months and 12 months after the deadline.
Reasonable excuse: HMRC may waive penalties if you have a genuine reason for missing the deadline (serious illness, bereavement, IT failures). Always submit as soon as you can and contact HMRC immediately if you cannot meet a deadline.
What are payments on account?
If your Self Assessment tax bill is over £1,000 and less than 80% was collected at source (e.g. through PAYE), HMRC requires you to make advance payments toward the following year's bill.
Each payment is 50% of the previous year's tax liability. So if you owed £4,000 for 2024/25, you pay £2,000 on 31 January 2026 and £2,000 on 31 July 2026 as advance contributions toward your 2025/26 bill.
If you expect your income to be significantly lower in the current year, you can apply to reduce your payments on account using form SA303 or through your Government Gateway account. If you reduce too much, HMRC will charge interest on the shortfall.