Corporation Tax Deadline: When Is Corporation Tax Due & How to File

HMRC & Compliance · 8 min read · Updated 2026-03-15

Understand when corporation tax is due, filing deadlines with HMRC, how to file your CT600, and penalties for late submission or payment.

Written by Krishna, Founder & HMRC-registered tax agent at TaxRoot.

When is corporation tax due for a March year end?

If your accounting period ends on 31 March, your corporation tax payment is due by 1 January of the following year (nine months and one day later). Your CT600 return must be filed by 31 March of the following year (twelve months after the end of the accounting period). For…

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