Corporation Tax Deadlines Calculator

Enter your accounting period to see the payment and filing dates, including the two returns needed for a period longer than 12 months.

Accounting period

Start date

End date

These are the company's first accounts The start date is the date the company was incorporated.

Pay Corporation Tax by

1 January 2027

In 90 days 9 months and 1 day after the period ends

File the CT600 by

31 March 2027

In 179 days

Accounts to Companies House by

31 December 2026

In 89 days

Company Tax Return

Return period	Days	Pay by	File by
01/04/2025 – 31/03/2026	365	1 January 2027	31 March 2027

Guide only. Dates are for a private company whose taxable profits are £1.5 million or less; larger companies pay Corporation Tax in instalments. Companies House deadlines change if the accounting reference date is shortened.

Guidance only. This calculator gives a general estimate and is not tax advice. Speak to your accountant before relying on these figures or making any decisions based on them.

When Corporation Tax is due

Corporation Tax is due nine months and one day after the end of the accounting period, so before the return itself is due. Companies with taxable profits above £1.5 million pay in instalments instead.

When the CT600 is due

The Company Tax Return is due 12 months after the end of the period the accounts cover.

Accounts longer than 12 months

A corporation tax accounting period cannot be longer than 12 months. If your accounts cover a longer period, such as a first period, you file two returns: one for the first 12 months and one for the rest. Each has its own payment date, but both returns are due 12 months after the end of the accounts.

Need to file the CT600?

This calculator is for guidance only. Tax Optimiser prepares the full corporation tax computation and files the CT600 and accounts with HMRC and Companies House.