Tax Diary: October to November 2025 Deadlines That May Still Matter

This tax diary highlights key UK tax deadlines that fall between October and November 2025. It is intended for taxpayers reviewing whether all obligations from this late-year period were dealt with correctly. As the calendar year draws to a close, unresolved filings or payments from this period can still result in interest, penalties, or HMRC follow-up if left unaddressed.

Key Tax and Payroll Deadlines for October and November 2025

• 1 October 2025 – Due date for Corporation Tax due for the year ended 31 December 2024.
• 19 October 2025 – PAYE and NIC deductions due for month ended 5 October 2025. (If you pay your tax electronically the due date is 22 October 2025.)
• 19 October 2025 – Filing deadline for the CIS300 monthly return for the month ended 5 October 2025.
• 19 October 2025 – CIS tax deducted for the month ended 5 October 2025 is payable by today.
• 31 October 2025 – Latest date you can file a paper version of your 2024-25 self-assessment tax return.
• 1 November 2025 – Due date for Corporation Tax due for the year ended 31 January 2025.
• 19 November 2025 – PAYE and NIC deductions due for month ended 5 November 2025. (If you pay your tax electronically the due date is 22 November 2025.)
• 19 November 2025 – Filing deadline for the CIS300 monthly return for the month ended 5 November 2025.
• 19 November 2025 – CIS tax deducted for the month ended 5 November 2025 is payable by today.

Why Late-Year Deadlines Still Matter

Tax obligations continue throughout the year. Where a return or payment was not completed on time, HMRC may continue to treat the matter as outstanding until it is resolved.

Reviewing late-year obligations can help ensure nothing is carried forward into the new year unintentionally, especially where issues are later identified during a review by a tax specialist in London or through HMRC compliance activity.

Common Obligations Around October and November

Deadlines during this period often relate to:

• VAT return submissions and payments
• PAYE and National Insurance reporting and payments
• Ongoing Self Assessment compliance
• Employer reporting obligations

Which obligations applied will depend on your circumstances, such as whether you were self-employed, an employer, or VAT-registered.

What Happens If a Deadline Was Missed?

If a tax deadline in October or November 2025 was missed, HMRC may have charged interest from the original due date. In some cases, penalties can also apply depending on the type of obligation and how late it was dealt with.

Even where no immediate penalty notice was issued, unresolved issues can still appear later through HMRC statements, reminders, or compliance checks, sometimes following a later review with a tax advisor in London.

Why It Is Worth Reviewing Now

Because October and November sit between busier points in the tax calendar, routine obligations are sometimes overlooked. Addressing any missed items now can help reduce the risk of problems later in the year. Reviewing this period can also make it easier to start the new year with a clear compliance position.

HMRC Guidance on Late Tax Obligations

HMRC explains how late filings and payments are handled, including interest and penalties, on GOV.UK.

Did You Miss Any October or November 2025 Deadlines?

Whether any action is required now will depend on which obligations applied to you at the time and whether they were dealt with correctly. For individuals and businesses in Wimbledon and nearby areas such as Mitcham and Cheam, CIGMA Accounting can review your position and confirm whether anything remains outstanding or needs to be addressed.