Last updated: 16 October 2026
Can you change your company’s year end?
Yes. You can change your company’s accounting reference date (year end) by filing form AA01 with Companies House, usually online and free of charge. You can shorten the current or previous accounting period as often as you like, but you can only extend it once every five years, and never to more than 18 months. The change must be filed before the deadline for filing the accounts for the period you’re changing.
Rules for changing the year end
| Change | Allowed? |
| Shorten current period | Yes, any number of times |
| Shorten previous period | Yes, if its accounts aren’t yet overdue |
| Extend period | Once every 5 years (with exceptions) |
| Maximum period length | 18 months |
Why change your year end?
- To align with a group or parent company
- To match a seasonal trading cycle
- To fit the accountant’s workload or your quiet time
- To align with the tax year, such as 31 March
Effect on corporation tax
Corporation tax returns cover periods of up to 12 months. If you extend your accounts to 18 months, you file two CT600s: one for the first 12 months and one for the remaining 6. Each has its own payment deadline, 9 months and 1 day after the end of that tax period.
Example
A company’s year end is 30 June. Its directors want to align with 31 March. In January 2026, they file AA01 to shorten the period ending 30 June 2026 to 31 March 2026. The next accounts cover 1 July 2025 to 31 March 2026, a 9-month period, and are due by 31 December 2026 (9 months after the new year end).
Filing deadlines after a change
If you shorten a period, accounts are due 9 months after the new year end or 3 months from the date you filed AA01, whichever is later.
Common mistakes
- Filing AA01 after the accounts deadline
- Extending more than once in five years
- Forgetting the CT600 split for long periods
- Not updating payroll or VAT periods
Records to keep
Keep the AA01 confirmation, board minutes approving the change and revised filing calendars.
Exceptions to the five-year rule
You can extend more than once in five years if the company is in administration, if the change aligns its year end with a parent or subsidiary in the UK or EEA, or if the Secretary of State approves. Companies House will reject an extension that breaks the rule, so check when the last extension was filed before applying.
Frequently asked questions
Does it cost anything?
No, filing AA01 online is free.
Do I need to tell HMRC?
HMRC gets the information from Companies House, but tell them if your CT periods change.
Does it affect VAT quarters?
No, VAT periods are separate; ask HMRC to change them if needed.
Can a dormant company change its year end?
Yes.
Planning considerations
Changing year end can bring forward or delay tax payments, affect the timing of capital allowances, and change which corporation tax rates apply to profits, so plan the change with your accountant.
Small companies
For a small company, a 31 March year end makes it easy to compare accounts with the tax year.
Related: accounts deadlines and penalties, submitting accounts and a CT return and dormant companies.
Talk to Accotax
Want this handled for you? Our team at Accotax can help with company year-end change. See our limited company accountants service, or contact us for a free, no-obligation quote.
This page is general guidance based on HMRC rules for the 2026/27 tax year, checked against gov.uk on 16 October 2026. It is not personal advice, so speak to an accountant about your own situation.
