Filing deadline for a new company’s first accounts

A new private company’s first accounts nearly always cover more than 12 months, and when they do the normal rule of nine months after the year end does not apply. Section 442(3) of the Companies Act 2006 sets the deadline as nine months from the first anniversary of incorporation (in effect 21 months from incorporation) or three months after the accounting reference date, whichever is later. For a public company the first figure is six months from the first anniversary, so 18 months from incorporation.

Why does a new company’s first financial period run for more than 12 months?

Under section 391(4) of the Companies Act 2006, a company incorporated today has an accounting reference date (ARD) of the last day of the month in which the anniversary of its incorporation falls. Section 391(5) then defines the first accounting reference period as the period of more than six months, but not more than 18 months, beginning with the date of incorporation and ending with that ARD.

Because the period starts on the day of incorporation itself and runs to the end of the anniversary month, an unaltered first period is always a little longer than 12 months. Companies House gives the example of a company incorporated on 6 April 2025: its first ARD is 30 April 2026, and 30 April every year after that. HMRC’s guidance on first accounts uses a company set up on 11 May, whose first accounts run to 31 May the following year and so cover 12 months and 3 weeks.

Subsequent periods are successive 12 month periods ending on the ARD (section 391(6)), so the special first year rule applies only once, unless the company changes its year end.

What exactly does section 442(3) require?

Section 442(2) gives the normal period for filing: nine months after the end of the accounting reference period for a private company, six months for a public company. Section 442(3) overrides that where the relevant period is the company’s first and is longer than twelve months. The period for filing is then:

• nine months (private) or six months (public) from the first anniversary of incorporation, or
• three months after the end of the accounting reference period,

whichever last expires. Companies House expresses the same rule as 21 months from incorporation for a private company and 18 months for a public company, or 3 months from the ARD if that is longer. Whether the private or public period applies depends on the company’s status immediately before the end of the accounting reference period (section 442(6)).

The first deadline is therefore tied to the incorporation date, not to the year end.

How do you count the months to the exact day?

Section 443 sets the counting rules. A period of months ends on the corresponding date in the appropriate month. If the starting date is the last day of a month, the period ends on the last day of the appropriate month, whether or not that is the corresponding date. If the starting date is the 29th or 30th and the period ends in February, it ends on the last day of February.

For a first accounts deadline the two starting dates are the first anniversary of incorporation and the ARD, so both need to be counted separately. Companies House counts to the exact day and records the date it receives acceptable accounts. A deadline falling on a Sunday or bank holiday is not moved, and accounts rejected and resubmitted after the deadline are late.

What does the calculation look like in practice?

Incorporated	First ARD	9 months from first anniversary	3 months after ARD	Deadline
6 April 2025	30 April 2026	6 January 2027	31 July 2026	6 January 2027
1 January 2025	31 January 2026	1 October 2026	30 April 2026	1 October 2026
31 May 2025	31 May 2026	28 February 2027	31 August 2026	28 February 2027

The second row is Companies House’s own example: a private company incorporated on 1 January 2025 with an ARD of 31 January 2026 has until midnight on 1 October 2026. The first row shows the usual trap. The company’s year end is 30 April, so in later years its deadline will be 31 January. For its first accounts, though, the deadline is 6 January 2027, nine months from the anniversary of 6 April 2026. A director who assumes 31 January 2027 will file 25 days late. In the third row the anniversary falls on a month end, so the month end rule in section 443(3) takes the deadline to the last day of February.

What if the first period is shortened or extended?

Shortening

A company can change its ARD by filing form AA01 online, through software or on paper. If the first accounts then cover 12 months or less, Companies House applies the normal periods: nine months from the new ARD for a private company. Section 442(4) adds that where a period is shortened by notice, the deadline is the later of that normal date and three months from the date of the notice.

Illustration only. A company incorporated on 15 March 2025 would normally have a first ARD of 31 March 2026 and a filing deadline of 15 December 2026. If in September 2025 it shortens its first period to end on 31 December 2025, the accounts cover less than 12 months and are due by 30 September 2026, about eleven weeks earlier than before.

Extending

A first period can be extended, but section 392(5) stops any accounting reference period exceeding 18 months unless the company is in administration. Companies House points out that the date of incorporation counts as the first day, so simply adding six months to the end of the period can take it past 18 months and the application will be rejected. It also confirms there are no additional restrictions on changing a first ARD, so the rule limiting extensions to once in five years does not bite.

Extending rarely buys much filing time. If the company incorporated on 6 April 2025 extends its first period to 30 September 2026, the three month limb gives 31 December 2026 and the 21 month limb gives 6 January 2027, so the deadline is still 6 January 2027. Any change must be made before the filing deadline for the period concerned; once accounts are overdue it is too late, and a change that produces a deadline already passed triggers an automatic penalty. The wider rules are in our guide to changing a company’s year end.

How does a long first period affect Corporation Tax?

The Companies House deadline is only half the picture. A Corporation Tax accounting period cannot be longer than 12 months, so where the first accounts cover more than 12 months the company may have to file two Company Tax Returns, with two payment deadlines. HMRC’s example is a company set up and trading from 11 May 2024 with an ARD of 31 May 2025: one return covers 11 May 2024 to 10 May 2025, a second covers 11 May to 31 May 2025, and the payment deadlines are 11 February 2026 and 1 March 2026.

The first Corporation Tax payment for that company falls on the same day as its Companies House deadline, 11 February 2026 (nine months from the first anniversary of 11 May 2025). The first set of accounts therefore needs to be finished with time to compute and pay tax, not just to file. A company that was dormant before it started trading may have a different pattern of returns; see the first Corporation Tax return after incorporation and our summary of Corporation Tax deadlines.

Can you get more time, and what if the deadline is missed?

Under section 442(5) Companies House can extend the period for filing on an application made before the deadline expires, but only for a special reason such as an unforeseen event, and section 442(5A) prevents any extension taking the deadline beyond twelve months after the end of the accounting reference period.

If acceptable accounts arrive late, a civil penalty is automatic, starting at £150 for a private company that is not more than one month late. Companies House lists “these are your first accounts” as a reason that is unlikely to succeed on appeal. The penalty bands are set out in Companies House accounts deadlines and penalties, and the appeal process in appealing a Companies House late filing penalty.

What mistakes do new companies make with their first accounts?

• Adding nine months to the first ARD instead of counting from the first anniversary of incorporation.
• Forgetting the month end rule, or counting from the wrong anniversary date when the company was incorporated late in a month.
• Shortening the first period to tidy up the year end without recalculating the new, earlier deadline.
• Extending the first period and assuming the deadline moves with it, or extending beyond 18 months counted from the incorporation date.
• Leaving the first accounts until the last week and having them rejected with no time left to correct them.

The simplest check is the company’s public record, which shows the date the next accounts are due, together with Companies House email reminders. The rest of the year’s dates are set out in our annual filing calendar for a small limited company.

Company directors can protect the business against the cost of an HMRC check with tax investigation insurance, which pays up to £100,000 of accountant’s fees with Solar Protect. Read how our cover works or get a quote.

Related Accountapedia entries

• Can you get an extension to file company accounts
• First statutory accounts for a new company
• Long first accounts: splitting into two tax returns
• Buying a ready made shelf company
• Accounts filing for an overseas company’s UK establishment

Sources

• legislation.gov.uk: Act 2006 c. 46, section 391
• GOV.UK: Life of a company part 1 accounts
• GOV.UK: First company accounts and return
• legislation.gov.uk: Act 2006 c. 46, section 442
• legislation.gov.uk: Act 2006 c. 46, section 443
• legislation.gov.uk: Act 2006 c. 46, section 392
• GOV.UK: Corporation tax accounting period
• GOV.UK: Print
• GOV.UK: Late filing penalties
• GOV.UK: Penalties for late filing

Reviewed by Christine Anderson, Broker, Solar Protect. Last reviewed 19 October 2026. Part of Accountapedia, the Solar Protect guide to UK tax and accounting. This page is general information, not personalised advice.