When is Corporation Tax due?

Corporation Tax is due 9 months and 1 day after the end of your accounting period. For a 31 March year end, that is 1 January. Companies with taxable profits over £1.5 million pay in instalments instead.

A company has three separate deadlines each year:

• Companies House accounts: 9 months after your year end (your first accounts are due 21 months after you incorporated).
• Corporation Tax payment: 9 months and 1 day after your year end.
• CT600 Company Tax Return: 12 months after your year end.

Example: for a 31 March 2026 year end, accounts are due by 31 December 2026, the tax is due on 1 January 2027 and the CT600 is due by 31 March 2027.

The payment date comes before the return date, so the tax has to be estimated and paid before the return is filed. Late filing penalties apply even if no tax is due, and HMRC charges interest on late payments. If the deadline falls on a weekend or bank holiday, the payment must reach HMRC by the last working day before it, unless you pay by Faster Payments.

Legislation: Taxes Management Act 1970, section 59D (when corporation tax is due and payable); Finance Act 1998, Schedule 18, paragraph 14 (filing date for the company tax return); Companies Act 2006, section 442 (period allowed for filing accounts).