Can You Change Your Company's Accounting Reference Date?

Ryan Patrick

Oct 8, 2026 • 12 min read

Yes. A UK company can change its accounting reference date (ARD), which is effectively the date used to determine when its financial year ends for Companies House purposes. A company can usually change its ARD to shorten or lengthen its current financial year or, in certain circumstances, change the immediately previous accounting period. The process is handled through Companies House, and the change must be made before the relevant accounts become overdue.

Changing the accounting reference date can be useful when a business wants its financial year to align with a parent company, group reporting cycle, seasonal trading pattern or preferred accounting timetable. However, there are important restrictions. You cannot simply move the year-end whenever you want, and extending a financial year beyond 18 months is generally prohibited unless the company is in administration. There are also specific rules governing how frequently an accounting period can be extended.

This guide explains how changing an accounting reference date works, when it makes sense, the restrictions that apply, and what the change means for Companies House and HMRC.

What Is an Accounting Reference Date?

An accounting reference date is the date that determines the end of a company's accounting reference period. In practical terms, it is the company's Companies House financial year-end. For a newly incorporated company, Companies House normally sets the first ARD as the last day of the month in which the anniversary of incorporation falls. Subsequent ARDs normally fall on the same date each year.

For example, if a company is incorporated on 15 June 2026, its first ARD will normally be 30 June 2027. A company can also prepare its accounts to a date up to seven days before or after the ARD. The ARD matters because it helps determine when the company's annual accounts must be delivered to Companies House.

Can You Change Your Company's Accounting Reference Date?

Yes. Companies House allows a company to change its accounting reference date for its current accounting period or the immediately previous accounting period. The change can either shorten or extend the accounting period. For example, a company with a 31 December year-end might decide that a 31 March year-end would work better.

It could potentially change its ARD so that its accounting period ends on 31 March instead. Likewise, a business with a 31 March year-end could potentially shorten its current accounting period to 31 December if it wants its financial year to align with a wider group. The important question is not whether a change is possible. It is whether changing the year-end is commercially useful and whether the company is still within the legal window to make the change.

Why Would a Company Change Its Accounting Reference Date?

There is no single reason for changing an ARD. Different businesses may have very different commercial motivations.

1. Aligning with a parent company

This is particularly common for UK subsidiaries of international groups. Suppose a UK company is owned by a parent company whose financial year ends on 31 December, while the UK subsidiary's year currently ends on 31 March. Maintaining different year-ends can create additional work when preparing consolidated management accounts.

Changing the UK company's ARD may make group reporting more straightforward. There are also specific rules that allow more frequent extensions in certain circumstances where a company is aligning its accounting reference date with a parent or subsidiary undertaking established in the UK.

2. Matching a seasonal business cycle

A business may prefer its year-end to fall immediately after its busiest trading period. For example, a retailer may find it more practical to close its financial year after its peak trading season rather than in the middle of it.

The same principle can apply to businesses with seasonal contracts, tourism operations, education services or other industries with significant fluctuations during the year.

3. Simplifying group reporting

A founder with several companies may want their businesses to share a common financial year-end. Having all companies close their accounting periods around the same time can make group-level reporting easier.

However, directors should consider the additional workload created by having multiple companies with the same reporting deadline. Sometimes staggering year-ends is actually more practical.

4. Aligning with an investor or reporting cycle

A growing startup may eventually need financial information for investors, lenders or a wider corporate group. A different year-end may fit more naturally with existing reporting arrangements.

That does not mean the company should change its ARD simply because an investor prefers a particular date. The accounting, tax and administrative implications should be considered first.

How Do You Change Your Company's Accounting Reference Date?

There are two main routes.

Online filing

Companies House allows companies to change their accounting reference date online. The online service is generally the quickest option. Companies House specifically recommends using the online service to update the information as quickly as possible.

Form AA01

The traditional paper route is Form AA01 — Change of Accounting Reference Date. The form can be used to change the accounting reference date for either the current or immediately previous accounting period. The form requires details including:

company number
company name
accounting period being changed
new accounting reference date
whether the period is being shortened or extended

Companies House says the form must be received within the period allowed for laying and delivering the accounts for the relevant accounting period. For most companies, online filing is simpler.

When Must You Change the Accounting Reference Date?

Timing is critical. You must make the change before the filing deadline for the accounts relating to the accounting period you want to change. Once those accounts are overdue, it is too late to change the ARD for that period. This creates a practical rule for directors: Change your year-end before your accounts become overdue, not after.

Suppose your accounts are due on 30 September. If you realise in August that your year-end should be changed, there may still be an opportunity to make the change. If you wait until October and the accounts are already overdue, changing the ARD will not rescue the company from the late filing position.

Can You Shorten Your Company's Financial Year?

Yes. A company can currently shorten its accounting reference period as often as permitted and by as many months as it chooses. Companies House guidance states that the minimum period by which a company can shorten its accounting period is one day. For example, a company might have a year-end of: 31 March 2027 and decide to move it to: 31 December 2026

That creates a shorter accounting period. Shortening the year can be useful when a business wants to bring its reporting date forward or align its accounts with a parent company's reporting timetable. There is an important upcoming change, however. Companies House guidance states that from 1 April 2028, a company will need to provide a business reason if it wants to shorten its accounting reference period more than once in five years. This change is subject to forthcoming regulations.

Can You Extend Your Company's Financial Year?

Yes, but the rules are stricter. A company can generally extend its accounting reference period to a maximum of 18 months from the start of that accounting period. The exception is where the company is in administration. There is also normally a once-every-five-years restriction on extending an accounting period. The restriction does not apply in certain circumstances, including where:

the company is in administration;
the Secretary of State has approved the extension; or
the company is aligning its accounting reference date with that of a qualifying parent or subsidiary undertaking established in the UK.

Example

Imagine a company's accounting period starts on 1 January 2026. It cannot simply extend the year-end to 31 July 2027 because that would create a period of 19 months. The statutory maximum is generally 18 months.

Companies House specifically warns directors not to simply add six months to an existing year-end, because doing so can accidentally produce an accounting period that exceeds the permitted maximum. The calculation needs to be based on the actual start date of the accounting period.

Are There Special Rules for a Company's First Accounting Period?

Yes. The first accounting period has different rules from later periods. For a new company, the first financial year starts on the date of incorporation. Its first ARD is normally the last day of the month in which its incorporation anniversary falls.

Companies House states that there are no additional restrictions when changing a company's first ARD. However, the first accounting period still cannot generally be extended beyond 18 months from incorporation. This can be useful for a newly incorporated business that has not yet established a convenient reporting cycle.

For example, a startup incorporated in January might decide early on that a December year-end would make more sense for its business or group reporting. Making that decision early can be considerably easier than changing the reporting structure several years later.

Does Changing the ARD Change the Accounts Filing Deadline?

Yes, generally. Companies House states that changing the company's year-end will normally change the deadline for filing its accounts, unless the change involves lengthening the company's first financial year. For a typical private company, annual accounts are normally due nine months after the end of the accounting reference period. Public companies generally have six months.

So changing the ARD can effectively move the company's annual accounts deadline. That is one reason directors should not treat the ARD as a cosmetic date. It is part of the company's statutory compliance timetable.

What If You Already Have an Extension to File Your Accounts?

Be careful. If you change your accounting reference date for a period where you already had an extension to the filing deadline, that extension will no longer apply. There is another important consequence.

If the new filing deadline has already passed by the time you change the ARD, the company will receive an automatic late filing penalty. This is another reason to calculate the consequences before submitting the change.

What Happens to Corporation Tax When You Change the ARD?

Changing the Companies House year-end will normally affect the company's Corporation Tax accounting period. HMRC needs to be kept up to date when the financial year has been shortened or lengthened. GOV.UK specifically states that companies must update their accounting period dates with HMRC after changing the financial year.

This is an important distinction: Changing your Companies House ARD does not mean you can ignore HMRC. The two systems are connected, but they are not identical. A change in the statutory accounts period can affect:

Corporation Tax accounting periods;
Company Tax Return periods;
Corporation Tax payment deadlines;
the periods covered by financial statements; and
the timing of your accountant's work.

For a company with complex tax affairs, changing the year-end should therefore be discussed with an accountant before the Companies House change is filed.

Does Changing the ARD Affect VAT?

Potentially, but not in the same direct way as Corporation Tax. Your VAT accounting periods are generally determined by your VAT registration and VAT return arrangements rather than simply following the company's Companies House year-end.

A change to the ARD therefore does not automatically mean your VAT return periods change. However, your accountant may need to consider the new year-end when preparing statutory accounts and reconciling VAT-related balances. This is a good example of why directors should avoid assuming that every UK compliance deadline moves together.

Can You Change Your ARD More Than Once?

Yes, but shortening and extending are treated differently. Currently, a company can shorten its accounting period as often as permitted, while extensions are normally restricted to once every five years. Exceptions can permit more frequent extensions in particular circumstances, such as administration, relevant group alignment or specific approval.

The practical takeaway is that repeatedly moving the year-end is not a sensible substitute for choosing an appropriate financial year. If a business finds itself wanting to change the ARD every year, there may be a broader accounting or management issue worth addressing.

A Realistic Example: Changing a Startup's Year-End

Consider Northstar Digital Ltd, incorporated with a 31 March year-end. The company is later acquired by an overseas parent whose financial year ends on 31 December. The directors decide that aligning the UK company's reporting date with the parent would simplify group reporting. They consider:

the current accounting period;
the date on which the accounts are due;
whether the period will be shortened or extended;
whether the change falls within the permitted rules;
the effect on Corporation Tax accounting periods; and
whether the change creates a new workload for the finance team.

They then submit the appropriate Companies House filing before the existing accounts deadline. The important point is that the decision is made before the deadline becomes a problem. That is the difference between a planned year-end change and a last-minute attempt to fix an overdue filing.

Should You Change Your Company's Accounting Reference Date?

A useful decision framework is:

Change it if:

your parent company's reporting year is different;
your group reporting would become materially easier;
your seasonal trading cycle makes another year-end more logical;
investors or management reporting require a different timetable;
the existing year-end creates unnecessary administrative complexity.

Think twice if:

the only reason is to postpone an imminent accounts deadline;
your accounts are already overdue;
you have not considered Corporation Tax consequences;
the change would create a difficult period for your accountant;
you are repeatedly changing the year-end without a clear business reason.

A year-end should serve the company's reporting needs rather than simply provide a way to move a deadline.

What Founders Should Check Before Changing the ARD

Before submitting a change, check:

Current ARD: What is the company's existing year-end?
Accounting period: What are the exact start and end dates?
Filing deadline: When are the current accounts due?
Direction of change: Are you shortening or extending?
18-month rule: Will an extension remain within the permitted maximum?
Five-year rule: Have you already extended the year-end within the relevant period?
Group structure: Is the change connected to a parent or subsidiary?
HMRC: What happens to the Corporation Tax accounting period?
Accountant: Can the accounts be prepared efficiently under the new timetable?
Companies House record: Has the new ARD been accepted and recorded?

This checklist is particularly useful for international founders, where a UK company may need to fit into a wider reporting structure. For global founders using IncorpUK, a UK company formation and management platform for global founders, the accounting reference date is one of the core dates worth tracking alongside the confirmation statement and tax calendar.

What Happens After You Change the ARD?

Companies House no longer sends paper letters confirming that an accounting reference date has changed. Instead, you can check the company's updated information through the Find and update company information service.

Once the new date is confirmed, update your internal compliance calendar. Do not rely solely on the date you originally submitted. The practical sequence should be: Submit change → confirm new ARD → recalculate accounts deadline → update HMRC/accounting records → update internal reminders. This simple process prevents an avoidable second mistake after successfully changing the year-end.

Frequently Asked Questions

Can I change my company's accounting reference date?

Yes. A company can change its accounting reference date for its current or immediately previous accounting period, subject to Companies House rules.

How do I change my company's accounting reference date?

You can change it online through Companies House or submit the appropriate AA01 form. Companies House also supports filing the change through compatible software.

Can I change my ARD after my accounts are overdue?

No. Companies House states that you cannot change an accounting reference date for a period where the accounts are already overdue.

How often can I extend my company's accounting period?

Normally, you can extend an accounting period only once every five years. Exceptions apply in certain circumstances, including administration, specific approval and some UK parent or subsidiary alignment situations.

How long can I extend my company's financial year?

An accounting reference period generally cannot be extended beyond 18 months from its start date, unless the company is in administration.

Can I shorten my company's accounting period?

Yes. Companies House currently allows companies to shorten their accounting reference period as often as permitted and by as many months as they choose. From 1 April 2028, a business reason will be required for shortening more than once in five years, subject to forthcoming regulations.

Does changing the ARD change my Companies House filing deadline?

Usually, yes. Changing the financial year-end generally changes the deadline for filing the company's accounts, unless the change is lengthening the first financial year.

Does changing the ARD affect Corporation Tax?

It normally can. Changing the company's year-end will usually affect its Corporation Tax accounting period, and HMRC needs to be updated about the new accounting period dates.

Can I change my ARD to avoid a late filing penalty?

No. If the accounts for the relevant period are already overdue, it is too late to change the ARD for that period. If a new deadline has already passed when the ARD is changed, a late filing penalty can apply.

Conclusion

A UK company can change its accounting reference date, and doing so can be sensible when the existing year-end no longer fits the company's commercial or reporting needs. The process is relatively straightforward: the company can make the change through Companies House online or by using Form AA01, provided the relevant accounting period has not become overdue.

The restrictions are where careful planning matters. Shortening an accounting period is generally flexible, while extending one is subject to the 18-month maximum and five-year rule, with specific exceptions. A change can also move your Companies House accounts deadline and affect your Corporation Tax accounting period.

For that reason, changing a year-end should be treated as a financial and compliance decision, not simply an administrative update. If the new date genuinely makes your company's reporting structure more efficient, changing the ARD can be worthwhile. If the only objective is to escape an approaching filing deadline, it is usually the wrong approach and may be too late anyway.