Tax Diary: December 2024 to January 2025 Deadlines That May Still Matter

This tax diary highlights key UK tax deadlines that fell between December 2024 and January 2025. It is intended for taxpayers reviewing whether all filing and payment obligations around the year-end and start of the new year were dealt with correctly.

January is a critical point in the tax calendar. Even where deadlines have passed, unresolved matters from this period can still result in penalties, interest, or HMRC follow-up action, particularly where issues were not reviewed at the time with a tax consultant in London or equivalent professional support.

Key Tax and Payroll Deadlines for December 2024 and January 2025

1 December 2024 – Due date for Corporation Tax payable for the year ended 28 February 2024.
19 December 2024 – PAYE and NIC deductions due for month ended 5 December 2024. (If you pay your tax electronically the due date is 22 December 2024).
19 December 2024 – Filing deadline for the CIS300 monthly return for the month ended 5 December 2024.
19 December 2024 – CIS tax deducted for the month ended 5 December 2024 is payable by today.
30 December 2024 – Deadline for filing 2023-24 self-assessment tax returns online to include a claim for under payments to be collected via tax code in 2025-26.
1 January 2025 – Due date for Corporation Tax due for the year ended 31 March 2024.
19 January 2025 – PAYE and NIC deductions due for month ended 5 January 2025. (If you pay your tax electronically the due date is 22 January 2025).
19 January 2025 – Filing deadline for the CIS300 monthly return for the month ended 5 January 2025.
19 January 2025 – CIS tax deducted for the month ended 5 January 2025 is payable by today.
31 January 2025 – Last day to file 2022-23 self-assessment tax returns online.
31 January 2024 – Balance of self-assessment tax owing for 2023-24 due to be settled on or before today unless you have elected to extend this deadline by formal agreement with HMRC. Also due is any first payment on account for 2024-25.

Why Year-End and January Deadlines Still Matter

Tax obligations do not fall away once a deadline passes. Where a return was not filed or a payment was not made on time, the obligation remains open until it is resolved.

For many taxpayers, January deadlines are when penalties are triggered and interest begins to accrue on unpaid tax, something often identified later through HMRC checks or a review by a tax specialist in London.

Common Obligations Around December and January

Deadlines during this period often relate to:

Self Assessment filing deadlines
Payment of tax due for the previous tax year
Payments on account for the current tax year, where applicable
VAT return submissions and payments
PAYE and National Insurance reporting and payments

Which obligations applied will depend on your circumstances, such as whether you were self-employed, a landlord, an employer, or otherwise required to file a Self Assessment return.

What Happens If a Deadline Was Missed?

Missing a January deadline usually results in an automatic late filing penalty. Interest is also charged on any unpaid tax from the original due date.

Further penalties can apply if delays continue. Even where no immediate action was taken by HMRC, outstanding issues may still be pursued later, often when matters are reassessed with a tax advisor in London or during a compliance review.

Check Whether You Missed Any Deadlines

Why It Is Worth Reviewing Now

Some taxpayers assume that once the new year has started, missed deadlines are no longer relevant. In practice, unresolved issues often resurface through HMRC statements, reminders, or compliance checks.

Reviewing whether all December 2024 and January 2025 obligations were met can help prevent unexpected costs or enforcement action.

HMRC Guidance on Late Tax Deadlines

HMRC provides guidance on late filing, late payment, penalties, and interest on
GOV.UK.

Did You Miss Any December 2024 or January 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 Hammersmith and nearby areas such as Brackenbury Village and Grove Park, CIGMA Accounting can review your position and confirm whether anything remains outstanding or needs to be addressed.

Need Help Staying on Top of Your December–January Tax Deadlines?

Important UK tax deadlines in December and January include VAT, PAYE/NIC, CIS returns and Self Assessment obligations. Specialist guidance can help you organise your filings, schedule payments and ensure you meet HMRC requirements on time to avoid penalties or interest.

Trusted guidance from London-based accountants, focused on accuracy, clarity, and compliance.

CIGMA Accounting

CIGMA Accounting Ltd is a forward-thinking accounting and tax firm based in London, dedicated to delivering high-quality compliance, tax planning, and business advisory services to entrepreneurs, landlords, and growing SMEs. With offices in Wimbledon and Farringdon, we combine local expertise with a tech-driven approach to simplify accounting. Our services include corporation tax filing, VAT compliance, HMRC investigation support, R&D tax credit claims, capital allowances optimisation, and bookkeeping automation. What sets CIGMA apart is our ability to blend traditional accounting rigour with AI-powered systems that reduce errors, save time, and provide real-time financial insights. Our team ensures that every client - from startups to high-net-worth individuals - receives a bespoke solution aligned with their growth goals. Whether you need strategic tax planning, help with HMRC disclosures, or a full outsourced finance function, CIGMA Accounting delivers clarity, compliance, and confidence.

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