Tax Diary: November to December 2023 Deadlines That May Still Matter

This tax diary highlights key tax deadlines that fell between November and December 2023 and is relevant for taxpayers who want to check whether any obligations from that period were missed.

Although these dates have passed, unresolved filing or payment issues linked to them can still result in penalties, interest, or HMRC follow-up action.

Key Tax and Payroll Deadlines for November and December 2023

• 1 November 2023 – Due date for Corporation Tax due for the year ended 31 January 2023.
• 19 November 2023 – PAYE and NIC deductions due for month ended 5 November 2023. (If you pay your tax electronically the due date is 22 November 2023.)
• 19 November 2023 – Filing deadline for the CIS300 monthly return for the month ended 5 November 2023. 
• 19 November 2023 – CIS tax deducted for the month ended 5 November 2023 is payable by today.
• 1 December 2023 – Due date for Corporation Tax payable for the year ended 28 February 2023.
• 19 December 2023 – PAYE and NIC deductions due for month ended 5 December 2023. (If you pay your tax electronically the due date is 22 December 2023).
• 19 December 2023 – Filing deadline for the CIS300 monthly return for the month ended 5 December 2023. 
• 19 December 2023 – CIS tax deducted for the month ended 5 December 2023 is payable by today.
• 30 December 2023 – Deadline for filing 2022-23 self-assessment tax returns online to include a claim for under payments to be collected via tax code in 2024-25.

Why Past Tax Diary Deadlines Are Still Relevant

Tax deadlines do not become irrelevant simply because time has passed. Where a return was not submitted or a payment was made late, the issue can remain open until it is resolved.

This means November and December 2023 deadlines may still affect you today if HMRC considers an obligation outstanding, something often identified later during a review by a tax specialist in London or through HMRC compliance activity.

Common Obligations Around November and December

Deadlines during this period often relate to:

• Self Assessment preparation ahead of the January filing deadline
• VAT return submissions and payments
• PAYE and National Insurance reporting and payments
• End-of-year compliance and reporting requirements

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 from November or December 2023 was missed, HMRC may have issued penalties or charged interest.

In some cases, penalties increase over time until the return is filed or the payment is made. Even where no immediate penalty was raised, HMRC may still pursue the issue later.

Why It Is Worth Reviewing Now

Some taxpayers assume older deadlines no longer matter. In practice, unresolved issues often resurface through HMRC reminders, statements of account, or compliance checks.

Reviewing whether all obligations from November to December 2023 were met can help avoid unexpected demands or enforcement action, especially where advice from a tax advisor in London was not taken at the time.

HMRC Guidance on Late Tax Deadlines

HMRC provides guidance on late filing, late payment, and the penalties and interest that may apply on
GOV.UK.

Did You Miss Any November or December 2023 Deadlines?

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