When are a new company's first accounts due?
A new private company whose first accounting period is longer than 12 months must file its first accounts within 21 months of incorporation, or within three months of the end of that period if that is later. If the first period is 12 months or shorter, the usual nine-month deadline after the period end applies.
Key facts
| First accounting reference date | The last day of the month in which the first anniversary of incorporation falls (Companies Act 2006, s391) |
|---|---|
| Length of the first period | More than 6 months and not more than 18 months |
| Deadline, first period of 12 months or less | 9 months after the period ends (6 months for a public company) |
| Deadline, first period over 12 months | The later of 21 months from incorporation (18 for a public company) and 3 months after the period ends (Companies Act 2006, s442) |
| Weekends and bank holidays | No extra time |
| Late filing penalty | £150 to £1,500 for a private company |
As at 25 October 2026.
Work out your first deadline in five steps
- Find the date of incorporation. It is on the certificate of incorporation and on the company's page of the Companies House register.
- Find the first accounting reference date. Take the last day of the month in which the first anniversary of incorporation falls, unless the directors have changed it.
- Measure the first period. Count from the date of incorporation to the accounting reference date. It is always more than 6 and at most 18 months.
- Apply the rule for that length. Up to 12 months: nine months after the period ends. Longer than 12 months: the later of 21 months from incorporation and three months after the period ends.
- Check the register. Compare your result with the due date Companies House shows for the company, and file before whichever is earlier.
A worked example
Companies House gives this example. A company is incorporated on 1 January 2025 with an accounting reference date of 31 January, so its first period runs from 1 January 2025 to 31 January 2026: 13 months.
| Test | Date |
|---|---|
| 21 months from incorporation | 1 October 2026 |
| 3 months after the first period ends | 30 April 2026 |
| Deadline (the later of the two) | 1 October 2026 |
Had the first period been 12 months or shorter, the deadline would simply have been nine months after it ended.
How the dates are counted
A deadline ends on the corresponding date of the target month (Companies Act 2006, s443). When the period ends on the last day of a month, the deadline is the last day of the target month: a period ending on 30 April is due on 31 January, while one ending on 4 April is due on 4 January.
Accounts count as delivered when Companies House receives acceptable accounts. Accounts it rejects do not stop the clock, so leave time to correct and resubmit.
Changing the first accounting reference date
The directors can shorten or extend the current period by notice to Companies House (Companies Act 2006, s392). An extended period may not exceed 18 months, and a period may normally be extended only once in five years. If the period is shortened, the deadline is the later of the normal deadline and three months from the date of the notice.
If the first accounts are late
The late filing penalty applies from the first set of accounts: £150 for a private company that is up to one month late, rising to £1,500 after six months. If the next year's accounts are late as well, the penalty for that year is doubled. See Companies House filing for the full table.
Frequently asked questions
Does a new company that has not traded still file first accounts?
Yes. A company that has been dormant since incorporation files dormant accounts, with the same deadline and the same late filing penalties as any other company.
Can I change my company's year end before the first accounts are due?
Yes. The directors can shorten or extend the first accounting reference period by notice to Companies House. An extended period may not be longer than 18 months.
Is the 21-month rule the same for a public company?
No. For a public company the deadline for a first period longer than 12 months is the later of 18 months from incorporation and three months after the period ends.
Does a first period of 13 months mean two Corporation Tax returns?
Yes. A Corporation Tax accounting period is never longer than 12 months, so the first 12 months and the remaining month each need a CT600. Both returns are due 12 months after the end of the 13-month period.
Sources
- Companies Act 2006, section 391
- Companies Act 2006, section 392
- Companies Act 2006, section 442
- Companies Act 2006, section 443
- Companies Act 2006, section 453
- Companies House: preparing and filing Companies House accounts
- Companies House: file your dormant accounts (AA02)
- Finance Act 1998, Schedule 18, paragraph 14
Prepare your statutory accounts
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Join the waitlistGeneral information about UK company law and tax, not legal or tax advice. The directors remain responsible for the accounts and returns they approve and file.