The AA01 form is used to notify Companies House of a change to a company’s accounting reference date (ARD), which determines the end of its financial year and when annual accounts must be filed.
In CAS 360 UK, you can update the accounting reference date directly from the company record and automatically generate the AA01 form for electronic or manual submission to Companies House.
When to File an AA01
An AA01 form must be filed when a company wants to:
Shorten its accounting period (can be done as often as required).
Extend its accounting period (generally only allowed once every five years, unless a valid exception applies).
Change its ARD for future financial years.
Important: The AA01 must be received by Companies House before the filing deadline for the existing period. Late filings may still require accounts based on the original ARD.
How to Prepare the AA01 – Change of Accounting Reference Period
| Navigating to Company from the Sidebar | |
| Select the Company from the list. |  |
| Select General Details |
From the General Details screen, expand the Company Dates section.
Update the Next Accounts Made Up To Date
Click
The following will be displayed:
| Button | Action |
|---|---|
| Save Only | Once saved, the updated date will show under General Details → Next Accounts Made Up To. |
| Prepare Forms | Opens the Change of Accounting Reference Date screen. The date will only be saved when you click Save & Prepare Documents within the Change of Accounting Reference Date screen. |
Change of Accounting Reference Date screen
When Prepare Forms is selected, the Change of Accounting Reference Date screen will appear. This allows you to confirm the new date and complete any additional questions required by Companies House.
Fields and Options
| Field | Description |
|---|---|
| Current Accounting Reference Date | Displays the existing accounting reference date. |
| New Accounting Reference Date | Enter the desired date (MM/DD/YYYY format). |
| Have you extended the accounting reference period more than once in five years? | Toggle ON if true – this reveals additional justification options below. |
If applicable, select one or more of the following:
The company is in administration
Special approval from the Secretary of State (requires entry of an Extension Authorised Code)
The change is to align with a parent or subsidiary company
The form is being submitted for an overseas company
Note: These options ensure compliance with Companies House restrictions on frequent ARD extensions. You must provide valid reasons if you’re extending more than once in a five-year period.
Finalise and File the AA01
Click Save & Prepare Documents to:
- Display the Document Production screen
- Save the new accounting reference date; and
- Generate the AA01 form and a Directors Minute/Resolution
Once the form are prepared, they be added to the company’s Documents screen where it can be lodged electronically.