There are specific rules that restrict changing a company’s year-end date, also known as the "accounting reference date". Initially, this is based on the date of incorporation. Under certain conditions, it’s possible to adjust the accounting year-end, which may offer trading or tax advantages for some businesses.

You can generally change the year-end for the current financial year or the one immediately preceding it. Altering the year-end will also adjust the deadline for filing accounts, except during a new company’s first financial year.

You can shorten the year-end date an unlimited number of times, but you can only extend it once every five years, with a maximum extension of 18 months. Extensions may occur more frequently under specific circumstances, such as if the company is in administration.

To request a change to an accounting reference date, you can use the Companies House online service for a quicker process or submit a postal version of the Change of Accounting Reference Date (AA01) form. Changes cannot be made for periods where accounts are overdue.

While there is no definitive reason to choose one date over another, various factors should be considered. The most common year-end dates are typically 31 December (to align with the calendar year) or 31 March (to align with the tax year).

Additionally, the Companies House rules stipulate that the year-end cannot be changed for any period where the accounts are overdue .