Tax Diary September/October 2025

1 September 2025 – Due date for corporation tax due for the year ended 30 November 2024.

19 September 2025 – PAYE and NIC deductions due for month ended 5 September 2025. (If you pay your tax electronically the due date is 22 September 2025)

19 September 2025 – Filing deadline for the CIS300 monthly return for the month ended 5 September 2025. 

19 September 2025 – CIS tax deducted for the month ended 5 September 2025 is payable by today.

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.