Every UK company must file annual accounts with Companies House — even if it is dormant or has never traded. When they are due depends on two things: whether this is the company’s first set of accounts, and its accounting reference date (ARD), the date its financial year ends. This article sets out the deadlines, how to work them out, and what happens to them when you change the year end.
The accounting reference date
A new company’s ARD is set automatically as the last day of the month in which the anniversary of incorporation falls. A company incorporated on 15 January 2025 has an ARD of 31 January, so its first financial year runs from 15 January 2025 to 31 January 2026. You can see a company’s ARD, and its next accounts due date, on its Companies House register page.
In Tax Optimiser each set of accounts belongs to an accounting period whose end date should match the ARD. If you are setting one up, see How to create an accounting period.
The deadlines
| Accounts | Private company | Public company |
|---|---|---|
| First accounts (covering more than 12 months) | 21 months after the date of incorporation | 18 months after the date of incorporation |
| Every later year | 9 months after the end of the financial year | 6 months after the end of the financial year |
A deadline falls on the corresponding date: a private company with a 31 March 2026 year end must file by 31 December 2026. For the example company above, first accounts to 31 January 2026 are due 21 months after 15 January 2025 — by 15 October 2026.
Heads up — the Companies House deadline is not the Corporation Tax deadline. HMRC wants the CT600 within 12 months of the end of the accounting period, and the tax paid 9 months and one day after it. For most small companies the Companies House accounts are due first.
Changing your accounting reference date
You can change the ARD for the current or immediately previous financial year by filing form AA01 before the accounts for that year are overdue. How it affects your deadline depends on which way you move it.
Shortening the year
You can shorten a financial year as often as you need to today. The new filing deadline is whichever is later of:
- the normal deadline worked out from the new ARD (9 months for a private company), or
- 3 months from the date you give Companies House notice of the change.
From 1 April 2028 you will need to give a business reason to shorten more than once in five years — see Preparing for April 2028.
Extending the year
A financial year cannot be extended to more than 18 months, and you can only extend once every five years unless the company is in administration, you are aligning with a parent or subsidiary undertaking, or the Secretary of State approves it.
If you can’t make the deadline
Companies House may grant an extension if something unexpected and outside your control stops you filing on time — you must apply before the deadline. Filing late brings an automatic civil penalty: see Companies House late filing penalties.
When are my first Companies House accounts due?
For a private company, 21 months after the date of incorporation. For a public company, 18 months after. After the first set, a private company has 9 months from the end of each financial year.
Do I have to file accounts if my company is dormant?
Yes. Every company must file annual accounts, even if it is dormant or has never traded. A dormant company can file simpler dormant accounts — see Filing dormant company accounts.
Can I change my company’s year end?
Yes, by filing form AA01 before the accounts for that year are overdue. You can shorten the year freely today, but can only extend it to a maximum of 18 months, and only once every five years in most cases.
What happens to my deadline if I shorten my accounting period?
It becomes the later of 9 months after the new year end (for a private company) or 3 months from the date you notified Companies House.