How to Change Your UK Company's Financial Year End

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 within 24–48 hours. 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.