When Is Corporation Tax Due in the UK (2026–27): Complete Guide for Companies
When is UK corporation tax due? Key deadlines for 2026/27, how to calculate it, what happens if you miss payments, and how to avoid costly HMRC penalties.
Every UK limited company must pay Corporation Tax on its profits. But when that tax is due, and how it aligns with your company's accounting year, often confuses new business owners.
Get it wrong, and you could face penalties, late payment interest, and even compliance flags with HMRC.
This guide explains when Corporation Tax is due, how to calculate your due date, what happens if you miss a payment, and how to pay it online safely.
Use our Corporation Tax Calculator to estimate your tax liability, and our how to pay HMRC online guide for detailed payment instructions.
For a complete overview of business taxes, our Self Assessment guide covers personal tax filing for company directors.
Corporation Tax is due 9 months and 1 day after your accounting period ends. The CT600 tax return must be filed within 12 months. Large companies pay in quarterly instalments.
What Is Corporation Tax
Corporation Tax is the business equivalent of Income Tax. It is paid by limited companies and certain organisations such as clubs or societies on their annual profits.
You pay Corporation Tax on trading profits, investment income, and capital gains if your company sells assets for a profit.
For the 2026/27 tax year, the main Corporation Tax rate is 25%. However, small companies may pay less under the Small Profits Rate, which is 19% on profits up to £50,000. Companies with profits between £50,001 and £250,000 benefit from marginal relief, which gradually increases the effective rate from 19% to 25%.
This dual-rate system was introduced to ensure smaller companies pay a lower rate while larger companies contribute more.
The Corporation Tax Calculator can help you estimate your liability based on your company's profits.
Corporation Tax is paid on trading profits, investment income, and capital gains. The rate is 19% for profits up to £50,000, 25% for profits over £250,000, and marginal relief applies between these thresholds.
Corporation Tax Rates for 2026/27
At the time of writing, the Corporation Tax rates for the 2026/27 tax year are as follows.
| Type of Company | Profit Range | Tax Rate |
|---|---|---|
| Small Profits Rate | Up to £50,000 | 19% |
| Marginal Relief | £50,001 to £250,000 | Gradual increase between 19% and 25% |
| Main Rate | Over £250,000 | 25% |
If your company has associated companies, the thresholds are divided by the number of associated companies. This means a company with one associated company has lower thresholds and may pay the main rate sooner.
Always check current rates with HMRC or use our calculator for an accurate estimate.
The Small Profits Rate is 19% on profits up to £50,000. The Main Rate is 25% on profits over £250,000. Marginal relief applies between these thresholds.
When Is Corporation Tax Due
The key rule is simple: your Corporation Tax is due 9 months and 1 day after the end of your accounting period.
For example, if your accounting year ends on 31 December 2025, your Corporation Tax payment is due on 1 October 2026.
The payment deadline and filing deadline are different. Payment comes before filing. Your Company Tax Return, known as the CT600, must be filed within 12 months of your accounting period end. For the same example, the CT600 filing deadline would be 31 December 2026.
These two dates are important to remember. Missing either one can result in penalties.
If your company's first accounting period is longer than 12 months, you may have two Corporation Tax accounting periods. This means two returns and two payments. HMRC will split the period into two parts, each with its own deadlines.
Corporation Tax is due 9 months and 1 day after your accounting period ends. The CT600 is due 12 months after the period ends. Payment comes before filing.
Corporation Tax Timeline Summary
| Task | Deadline | Based On |
|---|---|---|
| Pay Corporation Tax | 9 months and 1 day after year-end | End of accounting period |
| File Company Tax Return (CT600) | 12 months after year-end | HMRC online submission |
| Receive HMRC Notice to Deliver Return | Shortly after accounting year-end | Sent automatically |
| Account for tax in annual accounts | Within 9 months | Companies House alignment |
If your company's first year is longer than 12 months, you might have two Corporation Tax accounting periods. This means two returns and two payments, each with different due dates.
Corporation Tax payment is due 9 months and 1 day after year-end. The CT600 return is due 12 months after year-end. Payment comes before filing.
How to Work Out Your Corporation Tax Due Date
You can find your accounting period end in your HMRC online account, your Companies House registration, or your previous CT600 filing.
Once you know your accounting period end date, simply add 9 months and 1 day to determine your payment date.
Example 1 – Standard Accounting Year
Year ends: 31 March 2025
Payment due: 1 January 2026
Example 2 – Short Accounting Period (Start-up)
Year ends: 30 September 2025
Payment due: 1 July 2026
Example 3 – Extended Period (Over 12 months)
If your company's first accounts run from 1 January 2024 to 31 March 2025, which is 15 months, HMRC splits it into two periods:
- Period 1: 1 January to 31 December 2024
- Period 2: 1 January to 31 March 2025
You must file two tax returns with different due dates for each period.
Add 9 months and 1 day to your accounting period end date to find your payment deadline. Extended first accounting periods may be split into two periods with separate deadlines.
Corporation Tax Return Deadline (CT600)
Your Company Tax Return, known as the CT600, is due 12 months after the end of your accounting period.
It must include your company accounts, including profit and loss and balance sheet, a computation showing how the tax was calculated, and the CT600 form itself, which is the official declaration.
You file it online through your HMRC business tax account or approved accounting software. Most accountants will handle this for you, but it is ultimately your responsibility as a company director.
If you file your CT600 late, you will face penalties. These start at £100 for a single day late and increase over time.
For help with filing, our Self Assessment guide covers similar filing requirements for personal tax.
The CT600 tax return is due 12 months after your accounting period ends. File it online through your HMRC business tax account. Late filing triggers penalties.
How to Pay Corporation Tax Online
Paying HMRC is straightforward once you know your reference number.
You will need your 10-digit Unique Taxpayer Reference, your payment reference which is your UTR followed by the letter A, and the amount due.
| Method | Time to Clear | Notes |
|---|---|---|
| Online Bank Transfer (Faster Payments) | Same day / next day | Most popular method |
| CHAPS | Same day | For large payments |
| Debit Card | Same day | Pay via GOV.UK |
| Direct Debit | 3 to 5 working days | Use for recurring payments |
| Bacs | 3 working days | Slower method |
Always pay early if your due date falls on a weekend or bank holiday. This ensures your payment reaches HMRC on time.
Our how to pay HMRC online guide covers the payment process in detail.
Pay Corporation Tax through online bank transfer, debit card, CHAPS, Direct Debit, or Bacs. Use your UTR followed by the letter A as your payment reference.
What Happens If You Miss the Corporation Tax Deadline
If you pay late or file your CT600 late, HMRC applies penalties and interest.
Late Filing Penalties
| Delay | Penalty |
|---|---|
| 1 day | £100 |
| 3 months | Another £100 |
| 6 months | HMRC estimates bill and adds 10% |
| 12 months | Additional 10% of unpaid tax |
If you file late three times in a row, the £100 penalties increase to £500 each.
Late Payment Interest
Interest starts accruing from the day after your payment is due. At the time of writing, the interest rate is around 7.75%. Check the current rate on the GOV.UK website.
If you cannot afford to pay, HMRC may agree to a Time to Pay arrangement. This allows you to spread your payment over several months and avoid enforcement or penalty escalation.
Our how can I pay tax guide covers payment options in more detail.
Late filing penalties start at £100 and increase over time. Late payment interest applies from the day after the due date. Contact HMRC for a Time to Pay arrangement if you cannot pay.
Corporation Tax for Large Companies
If your taxable profits exceed £1.5 million, you must pay Corporation Tax in quarterly instalments rather than after year-end.
| Company Size | Taxable Profit | Payment Frequency |
|---|---|---|
| Small / Medium | Under £1.5m | 9 months + 1 day |
| Large | £1.5m to £20m | Quarterly instalments |
| Very Large | Over £20m | Earlier instalments |
Large companies usually make four payments throughout the accounting year. The final instalment falls 3.5 months after year-end.
If your company is approaching these thresholds, it is worth checking whether you need to switch to instalment payments.
Large companies with profits over £1.5 million must pay Corporation Tax in quarterly instalments. The final instalment is due 3.5 months after year-end.
How to Avoid Common Corporation Tax Mistakes
Several common mistakes can lead to penalties or overpaying tax. Understanding them helps you stay compliant.
| Mistake | Consequence | Fix |
|---|---|---|
| Paying late | Interest and penalties | Pay early via Faster Payments |
| Confusing filing vs payment deadlines | Missed obligations | Mark both dates in your calendar |
| Wrong reference number | Payment not matched | Always use UTR followed by A |
| Not claiming allowances | Overpaying tax | Include R&D, capital allowances, or losses |
| Missing two accounting periods | Double penalties | Keep HMRC and Companies House aligned |
You can verify deadlines easily through your HMRC Business Tax Account.
Our Corporation Tax Calculator can help you estimate your liability and plan for payment.
Common mistakes include paying late, confusing filing and payment deadlines, using the wrong reference, missing allowances, and misaligned accounting periods. Check your deadlines regularly.
Claiming Reliefs to Reduce Corporation Tax
Before paying, ensure you have applied all eligible deductions. Several reliefs can significantly reduce your Corporation Tax liability.
Annual Investment Allowance allows you to deduct up to £1 million on equipment purchases in the year of purchase. This is one of the most valuable reliefs for businesses investing in plant and machinery.
Research and Development (R&D) Relief provides up to 186% of qualifying costs for companies developing new products, processes, or software. This can significantly reduce your taxable profits.
Loss Relief allows you to offset past or future profits against losses, reducing your overall tax liability.
Patent Box offers a reduced rate of 10% on patent-related income for companies that hold qualifying patents.
These reliefs can significantly reduce your final liability before payment is due. Make sure your accountant claims everything you are entitled to.
Claim Annual Investment Allowance, R&D Relief, Loss Relief, and Patent Box to reduce your Corporation Tax liability. These reliefs can significantly lower your tax bill.
Example: Calculating and Paying Corporation Tax on Time
Bright Accounting Ltd's year ends on 30 June 2025.
- Accounting period: 1 July 2024 to 30 June 2025
- Profit: £90,000
- Tax rate: 25%
- Corporation Tax due: £22,500
- Payment deadline: 1 April 2026
- Filing deadline: 30 June 2026
If Bright Accounting files and pays before these dates, no penalties apply.
Use our Corporation Tax Calculator to estimate your own tax liability.
On a £90,000 profit, Corporation Tax is £22,500. Payment is due 9 months and 1 day after year-end. Filing is due 12 months after year-end.
Final Thoughts
Corporation Tax is a significant obligation for UK companies. The payment deadline is 9 months and 1 day after your accounting period ends. The CT600 tax return must be filed within 12 months. Missing either deadline can result in penalties and interest.
Large companies with profits over £1.5 million must pay in quarterly instalments. For smaller companies, the full amount is due in one payment.
Use reliefs such as Annual Investment Allowance, R&D Relief, and Loss Relief to reduce your tax liability. Keep accurate records of your accounting periods and deadlines to avoid late payment penalties.
All information in this guide is based on official HMRC and GOV.UK sources. Readers should verify current rates and deadlines directly with HMRC before making financial decisions, as rules may change after publication.
Written by
Sarah Collins
Sarah Collins covers self assessment, self-employed tax, side hustle income and small business finances in the UK.
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