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United KingdomGOV.UK

Overseas companies must post AA01 date-change form to Companies House

Overseas companies with a UK establishment must send paper form AA01 by post to the correct Companies House office; the notice procedure carries statutory timing, five-year and 18-month limits.

By Taxxa AI OyPublished 17 September 2026

Legal & Corporate

An overseas company with a UK establishment that changes its accounting reference date must send form AA01 on paper, by post, to the correct Companies House office. The online service remains available for other filers and is the fastest route: paper forms sent by post take longer to process.

Form AA01 gives notice to the registrar of a new accounting reference date under section 392 of the Companies Act 2006. The notice can take effect for the company's current accounting reference period and subsequent periods, or for the previous accounting reference period and subsequent periodsLegislation. It must state whether the period concerned is to be shortened, so it ends on the first occasion the new date falls after the beginning of the period, or extended, so it ends on the second such occasion.

Two statutory limits matter when choosing the new date. An extension notice is ineffective if given less than five years after the end of an earlier accounting reference period that was extended under the same sectionLegislation, subject to exceptions for group companies aligning dates, companies in administration, and cases where the Secretary of State directs otherwiseLegislation. And no accounting reference period may be extended beyond 18 months, except where the company is in administrationLegislation.

Timing also matters. Form AA01 must be received within the period allowed for laying and delivering the accounts for the current or the immediately previous accounting reference periodGOV, and a notice for a previous period cannot be given once the filing period for the accounts determined by that period has expiredLegislation. Because overseas companies with a UK establishment must now file on paper by post, they should allow for postal times so the notice arrives inside the window.

Companies House no longer sends paper letters confirming that an accounting reference date has changed. After filing, check the new date by searching for the company on the Companies House register rather than waiting for a letter that will not arrive.

The legal basis is sections 391 and 392 of the Companies Act 2006Legislation, governing accounting reference dates and their alteration by notice to the registrar.

If you file form AA01 for an overseas company with a UK establishment, post the paper form to the correct Companies House office in good time for the accounts filing window, then verify the new date on the Companies House register.

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