Corporation Tax Deadline and CT600 Submission Deadline Calculator
Enter the end of a UK company’s Corporation Tax accounting period to calculate its usual Corporation Tax deadline and CT600 submission deadline. The first is the payment date; the second is the Company Tax Return filing date.
Enter the accounting period end
What next?
Use the full filing calculator for Companies House accounts and confirmation statement dates, or get help with a CT600 and Corporation Tax position.
How the deadline calculator works
The usual Corporation Tax deadline is calculated by adding nine calendar months and one day to the accounting period end. The CT600 submission deadline is calculated by adding twelve calendar months.
Sources and limitations
The logic follows HMRC’s published ordinary deadlines. Use the UK Corporation Tax Calculator to estimate taxable profits, marginal relief and whether instalment payments may need review. This deadline tool does not automate quarterly instalment dates because those rules depend on additional facts and possible exceptions.
Corporation Tax deadline and CT600 submission deadline questions
Common points about Corporation Tax payment and CT600 submission dates.
When is Corporation Tax normally due?
For a company outside quarterly instalment rules, Corporation Tax is usually due 9 months and 1 day after the end of the accounting period.
When is the CT600 submission deadline?
The CT600 Company Tax Return is normally due 12 months after the end of the accounting period it covers. The payment deadline usually comes first.
Does a 31 March year end mean payment is due on 1 January?
For an ordinary 12-month accounting period ending 31 March, adding 9 months and 1 day produces 1 January of the following year, subject to quarterly instalments and any special circumstances.
What if the accounts cover more than 12 months?
A Corporation Tax accounting period cannot exceed 12 months, so long first accounts can require two Company Tax Returns and separate payment dates. Check the periods shown by HMRC.
Who may need quarterly instalment payments?
Companies with profits at an annual rate above the applicable threshold may need to pay by instalments. Associated companies can reduce the threshold, and exceptions can apply, so use HMRC guidance or obtain advice.