Corporation Tax deadline calculator: payment, return and accounts dates
Quick answer: Corporation Tax is due nine months and one day after the end of the accounting period, and the Company Tax Return (CT600) twelve months after it. Accounts go to Companies House nine months after the year end, or 21 months after incorporation for a first set covering more than 12 months. For a 31 March 2027 year end: tax by 1 January 2028, accounts by 31 December 2027, CT600 by 31 March 2028.
Written and reviewed by James Whitfield · Last checked against GOV.UK, HMRC and legislation.gov.uk · Editorial standards · Methodology. Estimates for planning only, not tax advice.
Use the calculatorWhat this tool covers
Enter the date your company's accounts end. If it is the company's first set of accounts, add the date the company was incorporated: a first period is often longer than 12 months, and a Corporation Tax period cannot be, so the tool splits it into two tax periods with two payment dates, the way HMRC does.
Our deadlines checklist covers everything a director has to do in the year. This page goes deeper on the Corporation Tax side: the split first period, quarterly instalments for large companies, the late filing penalties, and a calendar file you can import.
Read alongside: Limited company deadlines checklist · Corporation Tax 2026/27 · Forming a limited company: tax.
How each date is worked out
- Payment: nine months after the last day of the accounting period, plus one day. A period ending on the last day of a month is treated as ending on the last day of the ninth month after, so 31 May gives 1 March.14
- Company Tax Return: 12 months after the end of the period it covers. When accounts cover more than 12 months, both returns are due 12 months after the end of the accounts period, in line with GOV.UK's example.23
- Companies House accounts: nine months after the end of the financial year. First accounts covering more than 12 months are due 21 months after the company registered (or 3 months after they end, if later); a first period shortened to 12 months or less uses the normal nine months.59
- First period over 12 months: the first Corporation Tax period is the first 12 months from the start date; a second runs to the end of the accounts. Each has its own payment date. This assumes trading started on the day the company was set up.34
- Large companies (taxable profits at an annual rate over £1.5 million, the limit divided between associated companies) pay instalments instead: 6 months and 13 days after the period starts, then every 3 months, with the last 3 months and 14 days after the period ends.6
A normal 31 March year end
A company that has been trading for years, with accounts to 31 March 2027.
The tax is due three months before the return. Most companies pay on the payment date and file later, once the accounts are final.
A first period of 12 months and 3 weeks
GOV.UK's own example: set up and trading on 11 May 2024, first accounts made up to 31 May 2025.
The two payment dates match the ones GOV.UK gives for this case: 11 February 2026 and 1 March 2026. The accounts cover the whole 12 months and 3 weeks; the tax is split because a Corporation Tax period cannot exceed 12 months.34
A large company on a calendar year
Taxable profits over £1.5 million, accounting period 1 January to 31 December 2026, so tax is paid in four instalments.
These are the dates in HMRC's own example. Two instalments fall before the year ends, so the tax has to be estimated while the year is still running.6
Every figure in these examples is calculated by the same code as the calculator above, using the 2026/27 rates.
Where deadline planning goes wrong
Late filing penalties
| Time after the deadline | Penalty |
|---|---|
| 1 day late | £200 |
| 3 months late | another £200 |
| 6 months late | 10% of the unpaid tax (HMRC estimates the bill) |
| 12 months late | another 10% of any unpaid tax |
Late three times in a row: the £200 penalties become £1,000 each.2
| Time after the deadline | Penalty |
|---|---|
| Up to 1 month | £150 |
| 1 to 3 months | £375 |
| 3 to 6 months | £750 |
| More than 6 months | £1,500 |
Doubled if the accounts are late two years in a row.7
Corporation Tax deadline calculator: FAQs
When is Corporation Tax due?
When is the CT600 due?
When are first accounts due at Companies House?
Why do I have two Corporation Tax payments in my first year?
Do small companies pay Corporation Tax in instalments?
What is the penalty for late accounts?
Where these figures come from
The rates and rules on this page are drawn from the official UK government sources below, using the confirmed 2026/27 figures. Each link opens the relevant HMRC, GOV.UK or Companies House page in a new tab.
- Pay your Corporation Tax bill www.gov.uk/pay-corporation-tax
- Company Tax Returns, including penalties for late filing www.gov.uk/company-tax-returns
- Accounting periods for Corporation Tax www.gov.uk/corporation-tax-accounting-period
- Your limited company's first accounts and Company Tax Return www.gov.uk/first-company-accounts-and-return
- Accounts and tax returns for private limited companies www.gov.uk/prepare-file-annual-accounts-for-limited-company
- Pay Corporation Tax if you're a large company (instalments) www.gov.uk/guidance/corporation-tax-paying-in-instalments
- Annual accounts: penalties for late filing www.gov.uk/annual-accounts/penalties-for-late-filing
- Companies Act 2006, section 392: alteration of accounting reference date (18-month limit) www.legislation.gov.uk/ukpga/2006/46/section/392
- Companies Act 2006, section 442: period allowed for filing accounts (first accounts over 12 months) www.legislation.gov.uk/ukpga/2006/46/section/442
Every rate on this page was checked against these pages on 4 November 2026.