If you run a limited company in the UK, understanding your corporation tax deadlines is essential. Miss them and you face automatic penalties and interest charges. This guide explains the corporation tax deadline rules, when your payments are due, and what happens if you’re late.
What Is Corporation Tax?
Corporation tax is the tax that UK limited companies pay on their taxable profits. As of April 2023, the rate varies based on profit level. Companies with profits up to £50,000 pay 19% (the small profits rate). Companies with profits over £250,000 pay 25% (the main rate). Companies with profits between £50,000 and £250,000 pay a marginal rate between 19% and 25%, with marginal relief applied.
When Is My Corporation Tax Return Due?
The corporation tax return (form CT600) must be filed with HMRC within 12 months of the end of your accounting period. So if your company’s accounting year ends on 31 December 2024, your CT600 must be filed by 31 December 2025.
Note that this is the deadline for filing the return. The payment deadline is different.
When Do I Pay Corporation Tax?
For most small companies, corporation tax is due 9 months and 1 day after the end of your accounting period. This is earlier than the return filing deadline. So if your accounting year ends 31 December 2024, your corporation tax payment is due by 1 October 2025, but your CT600 isn’t due until 31 December 2025.
This catches many company directors out — they think the tax is due with the return, but actually the payment must be made up to three months before the return deadline.
Corporation Tax Deadlines for Common Accounting Year Ends
Here are the key deadlines for the most common accounting year ends:
- Year ending 31 March 2025: Payment due 1 January 2026 | Return due 31 March 2026
- Year ending 30 April 2025: Payment due 1 February 2026 | Return due 30 April 2026
- Year ending 31 May 2025: Payment due 1 March 2026 | Return due 31 May 2026
- Year ending 30 June 2025: Payment due 1 April 2026 | Return due 30 June 2026
- Year ending 31 December 2024: Payment due 1 October 2025 | Return due 31 December 2025
What Happens If You Miss the Corporation Tax Deadline?
Late Filing Penalties (CT600)
- 1 day late: £100 automatic penalty
- 3 months late: A further £100 penalty
- 6 months late: HMRC estimates your tax bill and adds a 10% tax-geared penalty
- 12 months late: A further 10% penalty on the unpaid tax
Late Payment Interest
If you pay your corporation tax late, HMRC charges interest on the unpaid amount. The current late payment interest rate is the Bank of England base rate plus 2.5%. With recent high interest rates, this can add up quickly. Always pay on time, even if you haven’t yet filed your return.
Quarterly Instalment Payments (QIPs)
Large companies (taxable profits over £1.5 million) must pay corporation tax in quarterly instalments throughout the year rather than as a single payment. This doesn’t affect most small and medium businesses, but if your profits are growing significantly, it’s worth being aware of.
How to Register for Corporation Tax
If you’ve recently set up a limited company, you need to register for corporation tax within 3 months of starting to trade. You can register online via HMRC’s website. ProKeeper can handle this registration on your behalf as part of our new company setup service.
Corporation Tax Planning — Reducing Your Bill Legitimately
Good tax planning can legitimately reduce your corporation tax bill. Key strategies include maximising your claim for allowable business expenses, using the Annual Investment Allowance (AIA) for capital expenditure, timing income and expenditure strategically, making pension contributions through the company, and claiming R&D tax credits if you’re carrying out qualifying research and development. ProKeeper’s accountants review your position annually to ensure you’re not paying more tax than you need to.
How ProKeeper Helps with Corporation Tax
Our Annual Accounts and Corporation Tax Return service handles everything from preparing your statutory accounts to filing your CT600 with HMRC. We always aim to have your accounts prepared well ahead of the deadline, giving you time to review, ask questions, and plan your tax payment. Contact us for a free consultation.
Don’t miss your corporation tax deadline. Get in touch with ProKeeper today and let our London accountants handle your tax return.