Corporation Tax Deadline & Penalty Dates

Corporation Tax is a key responsibility for UK companies, and meeting the relevant deadlines is essential to avoid interest and penalties. The timing of payments and filing obligations can vary depending on the size of the company and other factors.

This article provides a clear overview of the main corporation tax deadlines and payment dates, including rules for different company types, short accounting periods, group payment arrangements, and how these fit within HMRC’s self-assessment system.

Corporation Tax Payment Deadlines

The timing of the Corporation Tax payment deadline depends on the size of the company and the length of its accounting period (AP). HMRC applies different rules for companies based on whether they are classified as large or non-large, with specific provisions where accounting periods are shorter than 12 months.

Non-Large Companies

For companies that are not classified as large, Corporation Tax is payable as a single lump sum. It must be paid 9 months and 1 day after the end of the accounting period. To clarify, a company is classified as ‘non-large’ if its augmented profits do not exceed £1.5 million for the accounting period. This straightforward rule allows non-large companies to plan their payments in advance without the need for multiple Installments.

Example

If a company’s accounting period ends on 31 December 2024, the Corporation Tax payment must be made by 1 October 2025.

Large Companies

Companies with higher profits fall under a different regime. A company is classified as large for Corporation Tax purposes if its augmented profits for the accounting period exceed the £1.5 million threshold.

Augmented profits include taxable total profits and any exempt distributions (e.g., dividends) from non-group companies. Additionally, the £1.5 million threshold is time-apportioned for short accounting periods.

In such cases, the company is required to pay its Corporation Tax in four quarterly Installments, beginning during the accounting period itself.

What Are Augmented Profits?

Augmented profits consist of:

The company’s taxable total profits, and
Any exempt distributions received from non-group companies (e.g. dividends from investments outside the group).

Threshold Adjustment Rules

The £1.5 million threshold is not a fixed figure in all cases. It is adjusted to ensure fairness in the following ways:

Short Accounting Periods
The threshold is time-apportioned if the accounting period is shorter than 12 months.
Associated Companies
The threshold is divided by the number of associated companies that existed at the end of the previous accounting period.

Quarterly Installments- Timing and Calculation

Large companies are generally required to pay their Corporation Tax in four quarterly Installments. These payments are based on an estimate of the company’s tax liability for the current accounting period, allowing HMRC to collect tax progressively rather than as a lump sum at the end.

Installment Dates for a Standard 12-Month Accounting Period

For companies with a 12-month accounting period, the Installments are due on the 14th day of the following months after the start of the accounting period:

Month 7
Month 10
Month 13
Month 16

The payments are based on the estimated tax liability for the current accounting period. If the Installment date falls on a weekend or public holiday, the payment is due on the next business day.

Example

If the accounting period begins on 1 January 2025, the Installment payments will fall due on:

14 July 2025
14 October 2025
14 January 2026
14 April 2026

This schedule ensures that tax payments are spread across the accounting period and the months following its end.

Installment Payments for Short Accounting Periods

When the accounting period is shorter than 12 months, the Installment dates are adjusted accordingly:

The first Installment remains due by the 14th day of the 7th month after the start of the accounting period.
Subsequent Installments are due at three-month intervals.
The final Installment must be paid by the 14th day of the 4th month after the end of the accounting period.
In some cases, such as accounting periods of three months or less, the full tax liability is payable in a single Installment on the 14th day of the 4th month after the period ends, because applying the usual Installment schedule would mean the last Installment falls before the first.

Example 1

Sam plc has an 8-month accounting period from 1 May 2024 to 31 December 2024.

The first Installment is due by 14 November 2024 (7 months after 1 May 2024).
The second Installment is due 3 months later, on 14 February 2025.
The final Installment is due by 14 April 2025, which is the 4th month after the accounting period ends.

The Installments are split proportionally to cover the full estimated liability over these three payments.

Example 2

Beta Ltd has a 3-month accounting period from 1 January 2025 to 31 March 2025.

Because the accounting period is three months, the normal Installment dates would result in the last Installment being due before the first. Therefore, Beta Ltd must pay the full tax amount in one payment, due by 14 July 2025 (the 14th day of the 4th month after the period ends).

Calculating Installment Amounts

Each Installment payment is calculated by applying the following formula:

Installment Amount = Estimated Tax liability × n/Length of AP in months

Where:

Estimated Tax Liability = total Corporation Tax expected for the accounting period
n = number of months since the previous payment (usually 3)
Length of AP = total number of months in the accounting period

This formula ensures that Installments are proportionate to the length and timing of the accounting period, particularly where it is shorter than 12 months.

Example

Gamma Ltd has an 8-month accounting period from 1 April 2025 to 30 November 2025. Its estimated Corporation Tax liability is £640,000.

Using the formula above, the Installment payments would be calculated as follows:

First Installment (due 14 October 2025):
£640,000 × (3/8) = £240,000
Second Installment (due 14 January 2026):
£640,000 × (3/8) = £240,000
Final Installment (due 14 March 2026):
£640,000 × (2/8)=£160,000

The last Installment covers only 2 months as it falls less than three months after the second payment.

Exceptions to Quarterly Installments

Even if a company qualifies as large based on its augmented profits, it may be exempt from paying by Installments under certain conditions:

The Corporation Tax liability for the period is less than £10,000 (this threshold is adjusted proportionally for short accounting periods).
The company has become large for the first time during the current accounting period, provided that:

- It was not large in the previous accounting period, and
- Its augmented profits do not exceed £10 million for the current period (adjusted for short APs and associated companies).

These exceptions reduce the administrative burden on companies with smaller tax liabilities or those newly crossing the large company threshold.

Filing Deadline: Corporation Tax Return (CT600)

All UK companies must file a Corporation Tax Return (Form CT600) with HMRC to report on their taxable profits and calculate how much tax they owe. It is a legal requirement, and late filing can lead to interest and penalties.

When is the Corporation Tax Deadline for Filing?

The Corporation Tax return must be submitted by the later of:

12 months after the end of the company’s accounting period, or
3 months after HMRC issues a formal notice to file the return. If no notice is received, the filing deadline defaults to 12 months after the end of the accounting period.

Important

These deadlines refer to filing the return—not paying the tax. Corporation Tax is usually payable earlier (e.g. 9 months and 1 day after the year-end for most companies).

Example: Filing Deadline

ABC Ltd has an accounting period ending 31 December 2024. HMRC sends a notice to file the Corporation Tax return on 1 March 2025.

12 months after the year-end = 31 December 2025
3 months after the notice = 1 June 2025

Therefore, the filing deadline will be 31 December 2025, as it is the later of the two dates.

Method of Payment and Submission

All Corporation Tax payments and returns must be handled electronically in line with HMRC’s digital requirements.

Paying Corporation Tax

Corporation Tax must be paid electronically using an accepted HMRC payment method, such as:

Faster Payments
BACS or CHAPS (note: these may take up to 3 business days to process)
Online debit or corporate credit card
Direct Debit (if previously arranged)

Tip

Businesses should make payments well before the deadline to allow time for processing and ensure that funds clear into HMRC’s account on time. Late payments may attract interest charges and penalties.

Submitting the Corporation Tax Return

The Corporation Tax return (Form CT600) must be filed online through:

HMRC’s Corporation Tax digital service, or
Compatible accounting software(e.g., Xero, QuickBooks) approved by HMRC.

Paper returns are not accepted except in rare cases where HMRC has granted special permission (e.g. for insolvency or accessibility reasons).

Ensuring both payment and filing are completed electronically and on time is essential for avoiding penalties and maintaining good standing with HMRC.

Conclusion

Corporation Tax compliance involves more than just paying the correct amount—it also means meeting specific deadlines for both payment and filing. The rules differ depending on whether a company is classified as large or non-large, with large companies often needing to plan for quarterly Installments within the accounting period. Additional considerations, such as short accounting periods, associated companies, and exceptions for smaller liabilities, require careful attention to detail and timely action.

Staying informed about these requirements and using HMRC-approved digital systems for both payment and submission helps businesses avoid penalties and interest charges. With good planning and an understanding of the Corporation Tax framework, companies can manage their obligations efficiently and remain in good standing with HMRC.