When to Pay Corporation Tax: UK Deadlines Explained for 2026

What if the Corporation Tax date in your calendar is later than the actual payment deadline? If you’re unsure when to pay corporation tax, you’re not alone. The payment date is separate from the deadline for filing your CT600 return, and confusing the two can lead to late payment interest.

For many companies, Corporation Tax is due nine months and one day after the end of the accounting period, while the CT600 is due 12 months after it ends. You therefore have longer to file than to pay. Calculate both dates from the correct period end and include the payment in your cash flow planning.

This guide explains how to calculate the likely payment deadline, how it differs from the filing date, and which circumstances can change the timetable. It also covers quarterly instalments for larger companies and practical steps to consider if your business can’t pay on time. Clear dates and company specific tax compliance support can help you plan ahead with greater confidence.

When to pay Corporation Tax: the standard UK deadline

For most companies that aren’t required to pay by quarterly instalments, Corporation Tax is due nine months and one day after the end of the accounting period.

To work out when to pay corporation tax, start with the end date of the company’s Corporation Tax accounting period. The financial year label, such as 2025/26, doesn’t determine the payment date. The period end does. As a result, two companies can have different payment deadlines even if they describe their accounts using the same financial year.

For an overview of how Corporation Tax fits into the wider UK tax framework, see this guide to the UK Corporation Tax system. To check your company’s actual deadline, refer to its accounting records and the applicable HMRC guidance.

How to calculate your Corporation Tax payment date

First, identify the end date of the company’s Corporation Tax accounting period. Add nine calendar months and one day. For example, if the period ends on 31 December 2025, nine months later is 30 September 2026, making 1 October 2026 the illustrative payment deadline. Confirm the date against current HMRC guidance before scheduling payment.

Don’t rely on a year end date from memory. Check the company’s Corporation Tax records, particularly if it has changed its accounting date or has a shortened or otherwise unusual accounting period. Confirm which period the tax relates to before setting a reminder, as the period dates can affect the calculation.

Which companies use the standard payment timetable?

The standard timetable applies to most companies that aren’t subject to quarterly instalment payment rules. It doesn’t apply in the same way to every company or accounting period. Larger companies may need to pay in instalments, and associated companies or unusual circumstances can affect which rules apply.

If your company’s profits, group structure or accounting periods make its position less straightforward, check HMRC guidance or seek professional advice rather than assuming the standard date applies. A tax compliance review can help clarify your company’s obligations and the deadline to plan for.

Corporation Tax payment date vs CT600 filing deadline

Your Corporation Tax payment and your Company Tax Return (CT600) have separate deadlines. Both relate to the same accounting period, but filing the return doesn’t pay the tax you owe.

Companies need to track two Corporation Tax dates because payment is generally due before the CT600 filing deadline. The UK government’s official guidance explains the payment timetable, including instalment rules for companies that don’t use the standard schedule.

When is a company’s Corporation Tax return due?

For most companies, the CT600 must be filed within 12 months of the end of the Corporation Tax accounting period. Use the period end date as your reference point, then check the company’s filing obligations because specific circumstances can affect what applies. The return reports the company’s tax position. It isn’t a payment instruction.

What happens if the payment date comes before the return deadline?

A company may need to pay before it has finalised or submitted its CT600. For example, if its accounting period ends on 1 April 2025, the standard payment date would be 2 January 2026, while the general CT600 filing deadline would be 1 April 2026. This is an illustration, so confirm the dates that apply to your company.

Don’t wait until the filing date to consider how to fund the tax bill. Estimate the likely liability as reliable figures become available, then set money aside ahead of the payment deadline. Reviewing accounts information early can help you identify a potential shortfall and plan cash flow. Coombs’ statutory accounts preparation can support clear reporting, while tax compliance support can help clarify company specific obligations.

If you’re unsure which dates apply, consider discussing your company’s circumstances with an accountant. You can contact Coombs Chartered Accountants to discuss tax compliance and planning support.

Do quarterly instalments change when Corporation Tax is due?

Yes. Some larger companies don’t use the standard payment date. They pay Corporation Tax in quarterly instalments, which can mean payments fall before the end of the accounting period. Check the company’s taxable profits, accounting period and group position before deciding when to pay Corporation Tax.

Under current HMRC rules, quarterly instalments may apply when annual taxable profits exceed £1.5 million, or £20 million for the accelerated timetable, with these thresholds divided by the number of associated companies. The HMRC guidance on paying Corporation Tax explains the applicable rules. Eligibility can depend on more than a headline profit figure.

Which companies may need to pay Corporation Tax by instalments?

For a 12 month accounting period, the relevant profit thresholds are generally £1.5 million for large companies and £20 million for very large companies. Associated companies can reduce the threshold that applies to each company. There’s also a first year rule for some companies whose profits exceed the lower threshold, with an exception where profits exceed £10 million. Check HMRC guidance or ask a qualified accountant to assess your circumstances.

The accounting period length and company structure matter. Don’t assume that a company falls outside the rules because its own profits appear below a threshold before associated company adjustments.

How does an instalment schedule differ from the standard deadline?

Instalments can be due during the accounting period, rather than as one payment after it ends. For a 12 month period, large companies generally pay on the 14th day of months 7, 10, 13 and 16, while very large companies use an accelerated schedule on the 14th day of months 3, 6, 9 and 12. These dates aren’t a universal calendar. The accounting period length and company circumstances can affect the timetable, so confirm the dates that apply before arranging payments.

Directors should forecast taxable profits early and update the estimate as the company’s results develop. Cash flow forecasting can help set aside funds for expected instalments and reduce the risk of a payment date arriving before the money is available. Check eligibility and deadlines against the company’s records rather than relying on a general rule. Professional tax compliance support can help clarify the company’s position.

How to prepare for a Corporation Tax payment deadline

A clear process can help you estimate the bill, reserve cash for payment and avoid leaving arrangements until the last minute. Use this checklist to prepare for when to pay corporation tax:

• 1. Confirm the period dates. Check the company’s Corporation Tax accounting period and the payment deadline that applies. If the company has unusual periods or pays by instalments, verify the dates for its circumstances.
• 2. Estimate the liability. Use current financial records to build an estimate, then review it as the figures develop. The final tax calculation depends on company specific information.
• 3. Reserve funds. Set aside money regularly in line with the estimate and adjust the amount if expected profits change. This helps avoid relying on cash needed for other commitments.
• 4. Schedule the payment. Choose a payment method and check HMRC’s current payment instructions and processing times. Allow enough time for the payment to reach HMRC by the deadline.

What company records help estimate Corporation Tax?

Keep bookkeeping up to date and gather income records, details of allowable expenses and relevant year end figures. Management information can help you monitor performance before the accounts are finalised. Taxable profit may differ from the profit shown in company accounts because tax rules can require adjustments. Records alone won’t establish the final liability, so don’t treat an early estimate as a definitive calculation.

Accurate, timely figures make it easier to identify changes that could affect the expected bill. If you need help interpreting the company’s obligations, tax compliance support can help clarify your position.

How can a business plan cash flow around the deadline?

Instead of waiting until payment is due, use a cash flow forecast to map likely tax payments against expected income and other outgoings. Review it regularly and adjust the amount reserved as the company’s results change. This gives directors earlier visibility of a possible funding gap and more time to plan responsibly.

Before sending funds, confirm the payment reference and the latest HMRC instructions for your chosen method. Processing times can vary, so don’t assume a payment started on the deadline will arrive in time. If you’d like support planning for your company’s tax obligations and cash flow, contact Coombs Chartered Accountants to discuss your circumstances.

What to do if your company cannot pay Corporation Tax on time

If you expect your company to miss a Corporation Tax payment, act promptly. Contact HMRC to explain the company’s circumstances and discuss whether a payment arrangement may be possible. Be ready to outline what the company can afford, when it expects to pay and how it will meet future tax obligations. Don’t assume an arrangement is automatic. HMRC must agree to it, and contacting HMRC doesn’t remove any interest or other liability that may apply.

Even if you’re still confirming when to pay corporation tax, don’t wait until every figure is final before addressing a likely cash shortfall. Check the payment due, review available funds and expected receipts, and contact HMRC as soon as you understand there may be a problem. Keep a record of your communications and any agreed terms.

Could a late Corporation Tax payment lead to interest or penalties?

Late payment can have financial consequences. HMRC charges interest on overdue Corporation Tax, and the applicable rate can change, so check the current rate and rules in HMRC guidance. This is separate from penalties for filing a CT600 late. A payment arrangement, if agreed, doesn’t necessarily cancel interest or other amounts due. Check the specific consequences for your company rather than relying on a general estimate.

Keep payment and filing obligations separate. If the company can’t pay the tax, it should still check and meet its CT600 filing deadline where possible. If it may also miss that deadline, verify the current filing rules and consequences with HMRC.

When should a company speak to an accountant?

Seek advice if you’re uncertain about the relevant accounting period, an instalment schedule, the amount owed or the company’s ability to pay. These details can affect what to do next, and reliable records help build a clearer view of the company’s position. Tax compliance support can help clarify company specific obligations, while cash flow forecasting can help assess expected income, outgoings and upcoming tax payments.

Coombs Chartered Accountants supports businesses in Manchester, Stockport, Wilmslow and Alderley Edge with tax compliance and cash flow forecasting. If you’d like tailored advice on your company’s circumstances, you can contact Coombs Chartered Accountants.

Plan your Corporation Tax with confidence

Knowing when to pay corporation tax starts with the company’s accounting period end date. For most companies outside the quarterly instalment rules, payment is due nine months and one day later, while the CT600 return is generally due after 12 months. Keep both dates in your calendar, check whether instalments apply and estimate the liability early so you can set funds aside.

If your company may struggle to pay on time, contact HMRC promptly to discuss its circumstances. Any payment arrangement must be agreed, and interest or other consequences may still apply. Checking the company’s records and cash flow position early can help you decide what to do next.

Coombs Chartered Accountants supports businesses in Manchester, Stockport, Wilmslow and Alderley Edge with tax compliance, statutory accounts preparation and cash flow forecasting, alongside personalised financial guidance. Discuss your company’s tax deadlines with Coombs Chartered Accountants and plan ahead with a clearer understanding of your obligations.

Frequently Asked Questions

When is Corporation Tax due for a UK limited company?

For most UK limited companies outside the quarterly instalment rules, Corporation Tax is due nine months and one day after the end of the company’s accounting period. The period end date is the starting point for calculating the deadline, not the financial year label. Check the company’s accounting records and confirm whether any special circumstances or instalment rules change the timetable.

Is Corporation Tax due before the CT600 return deadline?

Yes. For most companies, Corporation Tax is payable nine months and one day after the accounting period ends, while the CT600 return is generally due within 12 months of that period end. These are separate obligations. Submitting the return doesn’t pay the tax. Estimate the likely bill and arrange payment by the payment deadline, even if the return hasn’t yet been filed.

How do I work out my company’s Corporation Tax payment date?

Find the end date of the Corporation Tax accounting period, then add nine calendar months and one day if the standard timetable applies. For example, an accounting period ending on 31 December 2025 gives an illustrative standard payment date of 1 October 2026. Check the company’s records and HMRC guidance, as shortened or unusual accounting periods and instalment rules can affect the applicable date.

Do all companies pay Corporation Tax nine months and one day after year-end?

No. The nine month and one day rule is the standard timetable for most companies, but some larger companies pay in quarterly instalments. The relevant accounting period and company circumstances matter, and associated company rules can affect whether instalments apply. Check the company’s position with HMRC or a qualified accountant rather than assuming the standard timetable applies.

When do large companies pay Corporation Tax in instalments?

Quarterly instalments may apply when annual taxable profits exceed £1.5 million. For very large companies, the accelerated instalment rules generally apply above £20 million. Both thresholds are divided by the number of associated companies, and other rules can affect eligibility. For a 12 month accounting period, large company instalments generally fall in months 7, 10, 13 and 16; very large company instalments fall in months 3, 6, 9 and 12.

What happens if a Corporation Tax payment deadline falls on a weekend or bank holiday?

Allow for the payment to reach HMRC by the deadline, rather than assuming it will be treated as on time because you initiated it that day. If a deadline falls on a weekend or bank holiday, HMRC generally expects cleared funds by the previous working day. Payment processing times depend on the method, so check HMRC’s current guidance and arrange payment in advance.

What should I do if my company cannot pay its Corporation Tax bill on time?

Contact HMRC as soon as you know the company may not be able to pay, explain its circumstances and ask whether an arrangement is possible. HMRC must agree to any arrangement, and interest or other consequences may still apply. If the deadline or amount is unclear, an accountant can help review the company’s position. Coombs Chartered Accountants supports businesses in Manchester, Stockport, Wilmslow and Alderley Edge.