Key Accounting Dates December 2025

byDaniel Greenaway/Published:23rd November 2025/inBusiness, Making Tax Digital, Running a business, Tax

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Staying ahead of your accounting and tax deadlines is one of the simplest ways to keep your business compliant and avoid any unwelcome surprises from HMRC. December might be dominated by year-end prep and the festive rush, but there are still several important dates that UK business owners, freelancers, and employers need to keep firmly on their radar.

Here are the key UK accounting and tax deadlines for December 2025, along with practical pointers to help you stay organised and compliant.

1st December 2025 – Corporation Tax payment: 28 February 2025 year ends

Businesses with a 28 February 2025 year end must ensure their Corporation Tax payment is submitted by 1 December 2025. This deadline falls nine months and one day after the close of your accounting period, and HMRC applies interest immediately if payment is late. Penalties can also be charged if delays continue, so it’s important to prepare well ahead of time.

To stay compliant, double-check your deadline using HMRC’s official Corporation Tax guidance: https://www.gov.uk/corporation-tax.

It’s also good practice to review your bookkeeping records, reconcile bank transactions, and ensure all year-end adjustments have been finalised before calculating what you owe.

If you use cloud accounting software, make sure it has generated the correct Corporation Tax figure based on your finalised accounts. Alternatively, working with a qualified accountant can help you spot reliefs, allowances, or adjustments you may have overlooked – ensuring accuracy and potentially reducing your tax bill.

1st December 2025 – Advisory fuel rates for company car drivers: new rates published

The new Advisory Fuel Rates (AFRs) for company car drivers take effect from 1 December 2025, and businesses using company vehicles should review these updates carefully. AFRs are set by HMRC to help employers reimburse employees for business mileage in company cars, or to calculate the taxable benefit when employees repay fuel costs. Using outdated rates can lead to incorrect reporting, potential overpayments, or compliance issues.

You can view the latest official rates on HMRC’s guidance page here: https://www.gov.uk/guidance/advisory-fuel-rates.

Make sure your payroll software, mileage claim forms, and internal policies are updated to reflect the new December 2025 rates.

If your business regularly reimburses mileage, it may also be worth reviewing whether a company car is still the most tax-efficient option compared to alternatives like cash allowances or electric vehicle schemes. Keeping your mileage and fuel policies aligned with HMRC rules helps ensure accuracy, reduces admin headaches, and supports cleaner financial reporting.

7th December 2025 – VAT return submission and payment (online): month or quarter-end 31 October 2025

If your business has a 31 October 2025 month-end or quarter-end, your VAT return and payment are due by 7 December 2025. This deadline applies to all VAT-registered businesses filing online, including those using Making Tax Digital (MTD) compliant software. Missing the submission or payment date can trigger HMRC’s late submission and late payment penalties, as well as interest on any outstanding VAT.

Make sure your bookkeeping is fully up to date before filing. This includes reconciling sales and purchase invoices, checking bank transactions, and reviewing any adjustments such as bad debt relief, reverse charge entries, or fuel scale charges. If you use MTD software, ensure that your VAT return has been generated correctly and submitted through an approved digital platform.

You can review HMRC’s VAT return guidance and digital filing requirements here:
https://www.gov.uk/vat-returns.

Taking the time to submit early gives you room to correct errors before the deadline and avoid avoidable penalties, especially during the busy December trading period.

19th December 2025 – PAYE, NIC and CIS payment (postal): month-end 5 December 2025

For employers and contractors operating PAYE, NIC, or CIS, the postal payment deadline for the period ending 5 December 2025 is 19 December 2025. This deadline applies if you are paying HMRC by post or using a payment method that requires additional processing time. Missing the postal deadline can lead to interest charges, late payment penalties, and potential issues with your PAYE or CIS compliance record.

Before submitting payment, ensure that your payroll for the period has been processed correctly and that all FPS (Full Payment Submission) and EPS (Employer Payment Summary) reports have been submitted to HMRC. For CIS contractors, double-check that deductions have been calculated accurately and that all subcontractor records are up to date.

You can find full guidance on PAYE and CIS payment deadlines on HMRC’s website:

If you prefer to avoid postal delays during the busy December period, consider switching to electronic payments, where the deadline is extended to the 22nd of the month. This also provides faster confirmation and reduces administrative risk.

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19th December 2025 – CIS return: payments made to subcontractors in the month to 5 December 2025

Contractors must ensure their CIS return for payments made to subcontractors up to 5 December 2025 is filed by 19 December 2025. This monthly return must include all payments made to CIS-registered subcontractors, along with any deductions withheld. Missing the deadline can lead to automatic late filing penalties starting at £100, with further charges applied the longer the return remains outstanding.

Before submitting your return, check that all subcontractors are correctly verified with HMRC, that payment and deduction statements are accurate, and that you have applied the correct deduction rates (gross, standard, or higher rate). Keeping well-organised records helps protect your business during compliance checks and minimises the risk of errors or under-reported deductions.

You can review HMRC’s full CIS filing requirements here:
https://www.gov.uk/what-you-must-do-as-a-cis-contractor.

Submitting early is especially wise in December, when postal delays, reduced staff availability, and year-end workloads can all increase the risk of last-minute problems.

22nd December 2025 – PAYE, NIC and CIS payment (electronic): month-end 5 December 2025

The electronic payment deadline for PAYE, NIC and CIS liabilities for the period ending 5 December 2025 is 22 December 2025. This applies to businesses paying HMRC via online banking, Direct Debit, Faster Payments, BACS, or other digital methods. Electronic payments give you a little extra breathing room compared to the postal deadline, but late payments can still result in interest charges and potential penalties.

Before making your payment, ensure that your payroll submissions are complete and accurate. This includes filing your FPS (Full Payment Submission) on time, submitting an EPS (Employer Payment Summary) where needed, and confirming that all deductions for CIS subcontractors have been calculated correctly. Errors in these reports can lead to mismatches in HMRC’s system, which may trigger compliance checks or payment discrepancies.

Full guidance on paying PAYE and CIS electronically can be found here:
https://www.gov.uk/pay-paye-tax.

With this deadline falling just before the Christmas break, it’s sensible to schedule your payment early to avoid delays caused by bank processing times or reduced staff availability. Doing so ensures you stay compliant and start the new year on the right foot.

30th December 2025 – Self Assessment: payment of 2024-25 tax via PAYE coding out online return submission

If you want HMRC to collect up to £3,000 of your 2024–25 Self Assessment tax bill through your PAYE tax code, your online return must be submitted by 30 December 2025. This option, known as “coding out”, allows HMRC to adjust your tax code for 2026–27 so the amount owed is collected gradually from your salary or pension – helping smooth out cash flow and avoid a large lump-sum payment.

To be eligible, you must already pay tax through PAYE, your return must be filed online, and your Self Assessment balance must fall within HMRC’s coding-out limits. Submitting after 30 December means you’ll need to settle your full bill by the standard deadline of 31 January 2026 instead.

You can review HMRC’s full guidance on paying tax through your tax code here:
https://www.gov.uk/pay-tax-through-your-tax-code.

Because this deadline falls during the festive season – a time when many taxpayers leave things until the last minute – it’s wise to file early. Doing so gives you time to correct any errors, gather missing information, and ensure you qualify for coding out if you want to spread the cost.

31st December 2025 – Corporation Tax returns: 31 December 2024 year ends

Companies with a 31 December 2024 year end must file their Corporation Tax return (CT600) with HMRC by 31 December 2025. This 12-month filing deadline is separate from the Corporation Tax payment deadline and applies to all companies, regardless of whether they made a profit, a loss, or had no trading activity during the accounting period. Missing the filing date will trigger automatic late filing penalties, which increase the longer the return remains outstanding.

Before submitting your CT600, ensure that your statutory accounts are finalised, all adjustments have been made (including capital allowances, R&D claims, and any disallowable expenses), and that your figures reconcile with your bookkeeping records. If you file through commercial software – now the standard requirement under HMRC rules – make sure your software is up to date and correctly configured for your reporting period.

You can read HMRC’s full Corporation Tax return guidance here: https://www.gov.uk/corporation-tax-returns.

Because this deadline falls on New Year’s Eve, businesses often face delays due to reduced staffing and holiday closures. Filing early helps avoid last-minute issues and ensures you remain fully compliant heading into the new year.

Final Thoughts

December may be a busy month for many UK businesses, but keeping on top of your accounting and tax deadlines is one of the simplest ways to stay compliant and avoid unnecessary penalties. From VAT and PAYE to Corporation Tax and Self Assessment deadlines, a little preparation now goes a long way toward ensuring a smooth end to the year and a stronger financial start to 2026.

If any of these deadlines apply to your business, now is the time to get organised, review your records, and make sure everything is filed and paid on time. And if you’d prefer expert support, we’re here to help.

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Accounting Wise supports businesses across the UK with clear, reliable, and proactive accounting services. If you want help managing your deadlines, preparing your accounts, or improving your financial processes, get in touch.

Let’s make your year-end stress-free.

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