Key Accounting Dates September 2025
Staying on top of your tax and compliance deadlines is essential for avoiding penalties and keeping your business finances in good order. September brings a variety of Corporation Tax, VAT, PAYE, NIC, and Construction Industry Scheme (CIS) deadlines plus updated advisory fuel rates and the due date for the Economic Crime Levy.
In this post, we’ve listed each key date for September 2025, explained what it means, and linked to official UK resources where you can find further guidance.
01/09/2025 – Corporation Tax payment: 30 November 2024 year ends
If your company’s accounting period ended on 30 November 2024, your Corporation Tax payment is due by this date.
Corporation Tax is normally payable nine months and one day after the end of your accounting period. Payment can be made by online banking, CHAPS, Bacs, or via your HMRC online account.
HMRC guidance: Pay your Corporation Tax bill
Tip: Always aim to submit your Corporation Tax return well before the payment deadline this ensures you have accurate figures and enough time to plan for the payment.
01/09/2025 – Advisory fuel rates for company car drivers: new rates published
HMRC publishes updated advisory fuel rates (AFRs) quarterly for company cars. These rates apply when:
- You reimburse employees for business travel in a company car, or
- Employees reimburse you for private use of a company car.
Using the correct AFR ensures there are no taxable benefits or unintended consequences for either the employer or employee.
HMRC guidance: Advisory fuel rates
Tip: Review your company car policy each time AFRs change to ensure expense claims and payroll deductions are accurate.
07/09/2025 – VAT return submission and payment (online): month or quarter-end 31 July 2025
If your VAT period ended on 31 July 2025, both your VAT return and payment are due by this date when filing online.
For most businesses, this is one month and seven days after the period end date. Late submissions or payments can trigger penalties under the VAT penalty system.
Tip: Automate VAT calculations through Making Tax Digital compliant software to reduce the risk of errors and late filing.
19/09/2025 – PAYE, NIC and CIS payment (postal): month-end 5 September 2025
Employers paying by post for the period ending 5 September 2025 must ensure HMRC receives payment by this date.
This covers:
- Pay As You Earn (PAYE) income tax deductions.
- National Insurance contributions (NIC).
- Construction Industry Scheme (CIS) deductions.
HMRC guidance: Pay PAYE to HMRC
Tip: Postal payments must arrive by the deadline – not just be sent by then. Factor in bank holidays and postal delays.
