---
title: Your accounting period and Companies House deadline
description: Your accounting period and Companies House deadline
---
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2. [Corporation Tax and Year-End](https://help.1stformations.co.uk/accounting-service/corporation-tax-and-year-end?hsLang=en-gb)
3. [Corporation Tax Fundamentals](https://help.1stformations.co.uk/accounting-service/corporation-tax-and-year-end?hsLang=en-gb#corporation-tax-fundamentals)
# Your accounting period and Companies House deadline
## And why your first year usually needs two CT600s
Your company has two separate filings each year: accounts to Companies House and a Corporation Tax return to HMRC. The deadlines are different.
### Companies House deadline
Accounts must be filed with Companies House within nine months of your accounting year end. For a year ending 31 March 2025, the Companies House deadline is 31 December 2025. We prepare and file your statutory accounts as part of our year-end service.
### CT600 deadline
Your Corporation Tax return (CT600) must be filed with HMRC within twelve months of the year-end. The Corporation Tax payment deadline is earlier (nine months and one day), so you pay first and file the return later.
### Why your first year usually needs two CT600s
A newly incorporated company's first set of accounts often covers slightly more than twelve months, because Companies House sets your first year-end to the last day of the month of your first anniversary. A company formed on 12 March 2025, for example, has a first period running to 31 March 2026. As a Corporation Tax accounting period can never exceed twelve months, HMRC splits this into two: a return for the first twelve months and a short return for the remaining days. So, you file one set of accounts to Companies House but two CT600s to HMRC for the first year, each with its own deadline and payment. We handle the split and the apportionment for you.
đź’ˇ **Good to know:** Your first year-end may fall sooner, or run slightly longer than you expect, and can create two Corporation Tax returns in the first year. We will confirm your specific accounting period and deadlines during onboarding, so nothing is missed.
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