What Is an Accounting Reference Date (ARD) and How Do You Change It? updated March 2026

Yes — every UK limited company has an Accounting Reference Date (ARD), which is the official end date of its financial year. It determines when you must prepare and file your annual accounts with Companies House and your Corporation Tax return with HMRC.

Updated March 2026: Your ARD is automatically set by Companies House as the last day of the month in which the anniversary of your company’s incorporation falls. For most companies, this creates a standard 12-month financial year, but you can change it (shorten or extend) using form AA01 — provided you act before the accounts filing deadline and follow the strict rules on extensions.

Changing your ARD is a common request among new directors who want to align their year-end with business cycles, tax planning, or group companies. At Filing Accounts, we regularly help clients change their ARD safely and on time while avoiding penalties. Contact us today for expert guidance and to handle the change for you.

What Exactly Is an Accounting Reference Date (ARD)?

The Accounting Reference Date (ARD) is the date on which your company’s financial year ends. It is also commonly called your year-end or accounting year-end.

Your annual statutory accounts must be prepared up to this date (or up to 7 days either side).
It directly affects your filing deadlines with Companies House and HMRC.
For a new company, Companies House automatically sets the first ARD as the last day of the month in which the first anniversary of incorporation falls.

Example:

Company incorporated on 15 March 2025 → First ARD is 31 March 2026 (last day of the month of the first anniversary).
Subsequent years would normally end on 31 March each year.

Official source: Companies House guidance on accounting reference dates

Why Does the ARD Matter for Your Limited Company?

Filing deadlines: Accounts must reach Companies House 9 months after the ARD (21 months for the first set of accounts).
Corporation Tax: Your CT600 return is due 12 months after the ARD, with payment due 9 months and 1 day after.
Business planning: Aligning your ARD with your busiest or quietest period makes accounting and tax planning much easier.
Group alignment: Many companies change their ARD to match parent or subsidiary companies.

Changing the ARD can give you extra time to prepare accounts or bring your year-end forward for better cash-flow management.

How to Change Your Accounting Reference Date (ARD) in 2026

You can change the ARD for the current financial year or the immediately previous one, but not if accounts for that period are already overdue.

Key Rules for Changing ARD (2026)

Shortening the period: Allowed as many times as you want.
Extending the period: Maximum 18 months (unless the company is in administration). You can only extend once every 5 years in most cases.
You cannot change the ARD if accounts are late.

Step-by-Step Guide: How to Change Your ARD

Decide on the new ARD Choose a sensible date that suits your business (many choose 31 December, 31 March, 30 June or 30 September).
Check you are still within the allowed window The change must be filed before the accounts filing deadline for the period you want to change.
Prepare Form AA01 This is the official “Change of accounting reference date” form.
File the form with Companies House
- Online (recommended – fastest): Use the Companies House WebFiling service or the online change service. You’ll need your company authentication code or GOV.UK One Login.
- By post: Download and complete form AA01 and send it to the address on the form.
Companies House processes the change Online changes are usually confirmed within days. You can then check the updated ARD on your company’s public record at Find and update company information.

Official form and guidance:

Pro tip: Always get director approval (via board resolution) before filing, even though the form only needs one signature.

What Happens After You Change the ARD?

Your new filing deadlines update automatically.
If you shortened the period, you may need to file accounts sooner.
If you extended it, you get extra time (up to 18 months maximum).
The change may also affect your Corporation Tax accounting period — check with HMRC if needed.

Common Mistakes When Changing ARD

Filing the change after the accounts deadline → rejected.
Trying to extend more than once in 5 years without qualifying exemption.
Forgetting that the change only applies to the current or previous period.
Not updating internal records or software after approval.

What Our Clients Say on Trustpilot

“Filing Accounts helped us change our ARD smoothly and explained everything clearly. Saved us from a tight deadline!” – Anonymous, February 2026 (5 stars)
“Professional and quick service for our accounting reference date change. Highly recommended.” – Mark T., March 2026 (5 stars)
“They handled the AA01 filing and made sure we stayed fully compliant.” – Sarah L., January 2026 (5 stars)

Our consistent 4.2/5 Trustpilot rating shows we deliver reliable support for these important changes.

Frequently Asked Questions

What is the default ARD for a new company? It is automatically set as the last day of the month in which the first anniversary of incorporation falls.

Can I change my ARD more than once? Yes for shortening. For extending, only once every 5 years in most cases.

Do I need an accountant to change my ARD? No — you can do it yourself online. However, professional help ensures you avoid mistakes that could delay your filing deadlines.

How long does it take for the change to be approved? Online submissions are usually processed within a few working days.

Will changing my ARD affect my tax obligations? It may shift your Corporation Tax deadlines — always check with HMRC or your accountant.

Official GOV.UK resources:

Need Help Changing Your Accounting Reference Date?

Changing your ARD is straightforward when done correctly, but the rules and deadlines are strict. Let Filing Accounts take the stress away — we’ll review your situation, prepare the AA01, and file it compliantly.

Contact us today or book a free consultation for expert support with your ARD change and all your Companies House filings.