How to Change Your UK Company's Financial Year End
By Ibrahem Almahawe
Key takeaways for Arab directors
- 1File form AA01 on Companies House WebFiling to change your accounting reference date
- 2You can shorten at any time; you can extend only once every 5 years
- 3Maximum accounting period length is 18 months
- 4CT payment deadline for an extended period: calculated from the end of the first 12 months, not the extended end date
- 5Common reasons to change: group alignment, tax year alignment, avoiding March congestion
Frequently asked questions
- How do I change my UK company's financial year end?
- You can change your company's accounting reference date (ARD) online using Companies House form AA01 via WebFiling. The change updates your future statutory accounts filing deadlines once accepted.
- How often can a UK company extend its financial year end?
- Under UK company law, you can extend your accounting reference date only once every five years, unless the company is in administration or has special approval from Companies House. You can, however, shorten an accounting period as often as you wish.
- Can I extend the financial year end if accounts are already overdue?
- No. Companies House does not allow a company to extend its accounting period if the filing deadline for that period has already passed. The extension form AA01 must be submitted before the statutory accounts deadline.
- How does extending the year-end affect Corporation Tax payment deadlines?
- If you extend an accounting period beyond 12 months (up to the maximum 18 months), HMRC requires two separate Corporation Tax returns (one for the first 12 months and one for the remaining period). The Corporation Tax payment deadline for the first 12 months remains nine months and one day after that 12-month mark.
Fileminder’s take, written for Arab UK company directors
Every UK limited company has a financial year end (accounting reference date, ARD). The default is the last day of the month in which the company was incorporated. You can change this using Companies House form AA01. For many Arab directors, the right year-end makes compliance simpler and planning more effective.
Common reasons to change your year end: align with the 5 April UK tax year (a 31 March year-end makes salary and dividend planning calculations cleaner); align multiple companies in a group to the same date for consolidated oversight; avoid a March/April accounting year-end when accountants are at their busiest (a September or October year-end gives more flexibility); extend a first accounting period to defer the first set of accounts and Corporation Tax deadline (up to 18 months from incorporation for a brand new company).
How to file AA01: log in to Companies House WebFiling at beta.companieshouse.gov.uk (or instruct your ACSP/accountant). Select 'Change of accounting reference date'. State the new ARD. Companies House confirms the change once processed. Once confirmed, your accounts filing deadline and CT return deadline adjust to the new dates. Notify HMRC by noting the change on your next CT return, or by calling the CT helpline if the change is urgent.
Rules and limits: you can shorten a company's accounting period at any time, any number of times. You can extend a period only once every 5 years (with some exceptions, such as when the company is in administration). The maximum length of any single accounting period is 18 months. You cannot extend a period if the current period is already past the normal filing deadline. If you extend, your accounts filing deadline moves but your Corporation Tax payment deadline is still calculated from the end of the first 12 months. HMRC splits long periods into a 12-month period and a short period for CT assessment.
When changing creates complications: shortening a period creates an additional set of accounts and CT return for the short period, adding compliance cost. For companies where VAT quarters are aligned to the year-end, you may need to adjust VAT periods with HMRC separately. Changing year-end mid-planning (e.g. after agreeing salary/dividend strategy for the year) can disrupt the timing of planned tax actions, always discuss with your accountant before filing AA01.
Written by
Founder of Fileminder, an AAT Licensed Accountant, and author of the eight-book International Taxation Series. Browse the books →
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Disclaimer
General educational guidance only, not legal, tax, accounting, immigration, investment or financial advice. We don't guarantee the information is complete, current or suitable for your situation. Always check official sources (GOV.UK, Companies House, HMRC, the relevant professional body) and speak to a qualified professional before acting. Last reviewed: July 2026.
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