Choosing a financial year end for your company

Your company’s financial year end, called its accounting reference date, is set automatically at the end of the month in which the first anniversary of incorporation falls. You can keep that date or change it at Companies House. Many owners pick 31 March to match the Corporation Tax year, or a date after their busiest season so stock is low and there is time to prepare the accounts.

How is a company’s year end set?

Companies House sets the first accounting reference date automatically. Its Life of a company guidance says the first date is “the last day of the month in which the anniversary of their incorporation falls”. Later year ends fall on the same day each year.

For example, a company incorporated on 6 April 2025 has a first year end of 30 April 2026. Its first accounts cover just over 12 months.

What deadlines does the year end set?

Your year end fixes your filing and payment deadlines at Companies House and HMRC.

The HMRC deadlines come from GOV.UK’s Company Tax Returns guide. For the full list, see our guide to company accounts filing deadlines.

How do accounts and Corporation Tax periods fit together?

A Corporation Tax accounting period “cannot be longer than 12 months”, according to GOV.UK. It is normally the same as the financial year in your accounts.

If your accounts cover more than 12 months, you must file two Company Tax Returns. This is common for a first year. A company formed on 15 November 2026 with a first year end of 30 November 2027 would have two tax periods: 15 November 2026 to 14 November 2027, and 15 November 2027 to 30 November 2027.

What should you think about when choosing a year end?

Choose a date that makes the accounts simpler and the tax cheaper to manage. These are the main factors:

• Corporation Tax rates. Rates are set for financial years running 1 April to 31 March. If your period straddles 1 April, GOV.UK says you work out how many days each rate applied and the tax due for each. A 31 March year end avoids that split.
• Your trading cycle. A seasonal business may pick a quiet month, when stock and work in progress are low and easier to count.
• Cash flow. A year end soon after a busy period gives you profits to fund the tax bill 9 months later.
• Your personal tax. Directors who take dividends often think in tax years ending 5 April. A 31 March year end lines the company up with that. Our guide to fiscal year vs tax year explains the difference.
• Your accountant’s workload. Avoid a deadline that lands in January, when accountants are busy with Self Assessment. Ask your accountant which dates suit them.
• Group companies. Subsidiaries usually share their parent’s year end so group accounts are easier to prepare.

Which year end suits you?

Use this list as a starting point, then check with your accountant:

• If you want the simplest tax position, choose 31 March.
• If you run a seasonal business, choose the end of your quietest month.
• If you are joining a group, align with the parent company.
• If you are happy with the automatic date, you do not have to do anything.

Can you change your company’s year end?

Yes. You can change it online with Companies House or on form AA01. GOV.UK’s rules are:

• Shortening: you can shorten your financial year “as many times as you like”.
• Extending: you can lengthen it to a maximum of 18 months, but only once every 5 years, unless the company is in administration, you are aligning with a subsidiary or parent company, or you have special permission from Companies House.
• Which year: you can only change the current financial year or the one immediately before it.
• Overdue accounts: you cannot change the year end when your accounts are overdue.

Changing the year end moves your filing deadline, except when you lengthen your first financial year. Any extension you already had for that year no longer applies. If the new deadline has already passed, you get a late filing penalty. See our guide to Companies House late filing penalties.

Changing your year end normally changes your Corporation Tax accounting period too, so you must tell HMRC. If you lengthen your year, GOV.UK says to contact HMRC before the original filing date.

What changes from April 2028?

Companies House has announced a limit on how many times a company can shorten its accounting reference period, as part of accounts filing changes from April 2028. The announcement does not give the exact limit. Until then, the current rules apply.

How to change your year end

1. Check your accounts are up to date. You cannot change the date while they are overdue.
2. Pick the new date and check whether it shortens or extends the year.
3. Check the new filing deadline has not already passed.
4. File the change online with Companies House or on form AA01.
5. Tell HMRC about the new Corporation Tax accounting period.

Use our Corporation Tax calculator to estimate the tax for your period.

Frequently asked questions

What is a company’s accounting reference date?

It is the last day of the company’s financial year. Companies House sets it automatically as the last day of the month in which the first anniversary of incorporation falls.

Can my company have a 31 March year end?

Yes. You can shorten or extend your first year to end on 31 March by filing the change with Companies House.

How often can I change my company’s year end?

You can shorten it as often as you like. You can extend it only once every 5 years, to a maximum of 18 months, unless an exception applies.

Does changing the year end change my Corporation Tax period?

Normally, yes. Tell HMRC the new dates, and remember a Corporation Tax period cannot be longer than 12 months.

Can a company’s first accounts cover more than 12 months?

Yes, up to 18 months. The deadline is 21 months after incorporation, and you file two Company Tax Returns for the period.