Key Dates for September and October 2026
Keeping track of tax and payroll deadlines can be difficult, particularly when you have several dates to remember throughout the year. Missing a deadline could result in penalties or interest, so it is important to make sure you are aware of what is due and when.
Here are some of the key tax and payroll dates to be aware of during September and October 2026.
Key Dates for September 2026
1 September 2026 – Corporation Tax
Corporation Tax is due for companies with accounting periods ending 30 November 2025.
19 September 2026 – PAYE and NIC
PAYE and National Insurance contributions are due for the month ended 5 September 2026. If you pay electronically, the deadline is 22 September 2026.
19 September 2026 – CIS Monthly Return
The deadline for filing the CIS300 monthly return for the month ended 5 September 2026 is 19 September.
19 September 2026 – CIS Tax
CIS tax deducted for the month ended 5 September 2026 is payable by 19 September 2026.
Key Dates for October 2026
1 October 2026 – Corporation Tax
Corporation Tax is due for companies with accounting periods ending 31 December 2025.
19 October 2026 – PAYE and NIC
PAYE and National Insurance contributions are due for the month ended 5 October 2026. If you pay electronically, the deadline is 22 October 2026.
19 October 2026 – CIS Monthly Return
The deadline for filing the CIS300 monthly return for the month ended 5 October 2026 is 19 October.
19 October 2026 – CIS Tax
CIS tax deducted for the month ended 5 October 2026 is payable by 19 October 2026.
31 October 2026 – Self Assessment
The deadline for filing a paper 2025/26 Self-Assessment Tax Return is 31 October 2026.
If you are unsure about a deadline or need support with your tax affairs, speak to a member of the Armstrongs team today.
