When is Corporation Tax Due?

Corporation Tax is a key part of running a limited company in the UK. But unlike VAT or PAYE, where HMRC sends regular reminders, the rules around Corporation Tax deadlines can catch people out—especially new company directors or those without an accountant. One of the most common questions we hear is simply, “When is Corporation Tax due?”

Paying Corporation Tax on time is crucial—but knowing when and how much to pay is only part of the picture. As your business grows, managing deadlines alongside allowances, reliefs and tax planning can become more complex. That’s where our limited company accountants come in. We support directors throughout the year, ensuring your accounts are prepared well ahead of the deadline and your Corporation Tax position is fully optimised. From forecasting your tax liability to advising on dividend planning, pension contributions and reinvestment, we help you avoid surprises and keep more of your profits working for your business.

In this guide, we’ll explain when your Corporation Tax payment is due, how it links to your financial year-end, what happens if you miss a deadline, and how to avoid common timing mistakes. Whether you’ve made a small profit or are navigating marginal relief, knowing your company’s tax timeline is essential.

What is the Deadline to Pay Corporation Tax?

For most UK limited companies, Corporation Tax must be paid within 9 months and 1 day after the end of your accounting period (also called your ‘financial year-end’).

For example:

• If your company’s accounting year ends on 31 March 2024, your Corporation Tax payment is due by 1 January 2025.

It is important to note that this is the deadline for paying the tax, not for submitting the return. You must pay the tax before you submit your CT600 (Company Tax Return), not the other way around.

Do I Get a Bill or Reminder from HMRC?

No—HMRC does not send out a bill for Corporation Tax. It is your company’s responsibility to:

• Work out how much Corporation Tax is due

• Pay it by the deadline

• File the Company Tax Return (CT600) within 12 months of your year-end

Even if your company made no profit or is dormant, you may still be required to file a return or notify HMRC. Ignoring this process can lead to penalties, even when no tax is owed.

What is the Deadline to File the Corporation Tax Return?

You must file your Company Tax Return within 12 months of the end of your accounting period. However, since your payment is due three months earlier, you’ll often need to prepare your accounts and tax calculation well before this deadline.

To recap:

• Corporation Tax payment deadline: 9 months and 1 day after year-end

• Corporation Tax return deadline: 12 months after year-end

Planning ahead ensures you have time to calculate tax accurately and avoid interest charges.

How Do I Know My Accounting Period?

Your accounting period usually matches your company’s financial year, as defined at Companies House when the company was formed. Most companies choose a 12-month period, ending on dates like 31 March or 31 December.

If your company’s year-end changes, or if you have a shorter first accounting period (common in your first year), HMRC may expect two returns. It’s best to confirm your key dates through your HMRC online account or by checking with your accountant.

Still working out what you owe? See how to calculate corporation tax.

Do All Companies Follow the Same Deadline?

The 9-month and 1-day rule applies to most small and medium-sized companies. However, if your company earns taxable profits of more than £1.5 million, you will usually need to pay in instalments, starting within six months of the start of your accounting period. This system is known as quarterly instalment payments.

The threshold is shared between associated companies. So, if you control multiple businesses, the £1.5 million is divided equally between them, which could bring smaller companies into the instalment regime sooner than expected.

What Happens if You Pay Corporation Tax Late?

Paying Corporation Tax after the deadline triggers interest charges. HMRC applies daily interest from the day after your due date until the tax is paid in full. The current interest rate is 7.75% per annum, though this can change.

While there’s no fixed penalty just for a late payment, penalties will apply if your Company Tax Return is also filed late. This starts at £100 and increases the longer it remains outstanding.

If you know you will struggle to pay on time, it’s important to contact HMRC early to request a Time to Pay arrangement. This can help you avoid enforcement action and manage repayments in instalments.

Need help making the payment itself? Read how to pay corporation tax.

Real-World Example

Let’s say your company’s financial year ends on 30 June 2024. Your deadlines will be:

• Corporation Tax payment due: 1 April 2025

• CT600 return due: 30 June 2025

Ideally, your accountant should prepare your accounts and Corporation Tax calculation in early 2025 so you can review and pay the tax before April. Waiting until the return deadline in June would already be too late to avoid interest.

Tips to Stay on Top of Corporation Tax Deadlines

• Mark your calendar for both payment and return dates

• Prepare accounts early, especially if you want to plan dividend withdrawals or reinvest profit

• Use accounting software like Xero, QuickBooks or FreeAgent to track profits in real time

• Work with an accountant who will handle deadlines, submissions and correspondence with HMRC for you

• Avoid last-minute surprises by setting aside tax money monthly

Final Thought

Corporation Tax isn’t just about how much you owe, it’s also about when you pay it. Missing the payment deadline by even one day can lead to interest charges, and failing to file your return can result in penalties. By understanding your company’s accounting period and acting early, you can avoid stress and ensure your business stays on the right side of HMRC.

If you run a small or newly formed company, it’s easy to assume Corporation Tax is something you only worry about once a year. But getting it wrong—even unintentionally—can lead to costly penalties and interest. Our small company accountant service is designed to take the pressure off. We help smaller businesses stay on top of their responsibilities, with straightforward advice, accurate filing, and a focus on making the most of every tax-saving opportunity. Whether this is your first return or you’re just tired of last-minute stress, we’ll guide you through the entire process with clarity and care.

If you’d like to explore related tax content, check out our Corporation Tax Help hub.