When you incorporate a company at Companies House, your accounting reference date (ARD) is automatically set to the last day of the month in which your incorporation anniversary falls. You do not have to keep it. Choosing a different year-end date can have real benefits for tax planning, cash flow and administrative convenience.
What is the accounting reference date?
Your accounting reference date is the date your company’s financial year ends. All your annual filings are based on this date:
| Filing | Deadline |
|---|---|
| Annual accounts to Companies House | 9 months after year end |
| Corporation Tax payment to HMRC | 9 months and 1 day after year end |
| CT600 (Company Tax Return) to HMRC | 12 months after year end |
For example, if your year end is 31 March, your accounts are due by 31 December, your Corporation Tax payment by 1 January, and your CT600 by 31 March the following year.
Common year-end dates and why businesses choose them
| Year-end date | Why it is popular |
|---|---|
| 31 March | Aligns closely with the UK tax year (5 April), simplifying personal tax planning for directors |
| 5 April | Exact match with the personal tax year |
| 31 December | Calendar year end, useful for international groups or businesses that follow the calendar year |
| 30 September | Six months offset from the tax year, spreading administrative workload |
| 30 June | Popular with businesses that want to avoid the busy January-March period for accountants |
There is no single “best” date. The right choice depends on your specific circumstances.
Tax planning advantages
Aligning with the tax year (31 March or 5 April)
A 31 March year end is the most popular choice for UK small companies because it aligns with the tax year. This makes it easier to plan your director’s salary and dividends since you know your company’s profit before the personal tax year ends.
With a 31 March year end, you can see your company’s full-year results and then decide how much dividend to vote before 5 April. This lets you stay within your preferred tax band.
Deferring Corporation Tax
Your Corporation Tax payment is due 9 months and 1 day after your year end. By choosing a year-end date that falls later in the tax year, you defer when the payment is due.
For example:
| Year end | CT payment due | Deferral vs 31 March |
|---|---|---|
| 31 March | 1 January following year | Baseline |
| 30 June | 1 April following year | 3 months later |
| 30 September | 1 July following year | 6 months later |
| 31 December | 1 October following year | 9 months later |
A later payment date gives you longer to hold onto cash, which matters for businesses with tight cash flow.
Timing capital expenditure
If you are planning a major purchase that qualifies for the Annual Investment Allowance, your year-end date determines which accounting period the deduction falls into. Buying equipment just before your year end gives you the tax relief in that period rather than waiting another 12 months.
Cash flow and seasonal businesses
If your business has a strong seasonal pattern, think about when your profits and cash are highest.
A year end that falls during your peak trading period means you are trying to prepare accounts while you are busiest operationally. A year end during your quiet period gives you and your accountant time to focus on the accounts without competing demands.
| Business type | Suggested year end | Reason |
|---|---|---|
| Retail (Christmas peak) | 31 January or 28 February | Accounts prepared after the busy season |
| Tourism / hospitality | 31 October or 30 November | After summer season |
| Construction | 31 March | Aligns with industry and government contracts |
| B2B services | 31 March or 30 June | Flexible; choose based on client billing cycles |
Avoiding the busy season
Accountants are busiest between January and April, when they are handling Self Assessment deadlines (31 January), year-end accounts for 31 March year ends, and the start of the new tax year. If you choose a year end that falls outside this period (such as 30 June or 30 September), you may find it easier to get your accountant’s attention and potentially negotiate lower fees.
Your first accounting period
When you first incorporate, your initial accounting period can be longer or shorter than 12 months. Companies House allows a first period of up to 18 months, though for Corporation Tax purposes, HMRC splits any period longer than 12 months into two.
This means you might file one set of annual accounts but two Company Tax Returns. Read more about this in our guide to year-end accounts.
How to change your year-end date
You can change your accounting reference date by filing a form AA01 with Companies House. This can be done online and takes effect immediately.
Rules for changing
- You can extend your accounting period to a maximum of 18 months from the start of the period
- You can shorten your accounting period at any time
- You can only extend your year end once every five years (unless you are an overseas company, or you are subject to an administration order, or Companies House grants special permission)
- The change must be filed before the deadline for the current period’s accounts
Shortening vs extending
| Action | Effect | Use case |
|---|---|---|
| Shorten | Next accounts cover fewer than 12 months | Moving year end earlier (e.g. from December to March) |
| Extend | Next accounts cover more than 12 months | Moving year end later (e.g. from March to December) |
If you shorten, you may need to file accounts sooner than expected. Plan ahead.
Notifying HMRC
When you change your accounting reference date at Companies House, HMRC is not automatically notified. You should write to HMRC to confirm the new date so your Corporation Tax records are updated. If you file your CT600 for the new period without notifying them first, the system may not recognise the period and you could receive a late filing penalty in error.
Group companies and associated companies
If your company is part of a group, aligning year-end dates across all group companies simplifies consolidated accounts and group relief claims. Losses can only be surrendered between group companies that share an overlapping accounting period, so different year ends create complications.
If you have associated companies (companies under common control), the Corporation Tax small profits thresholds are divided by the number of associated companies. Having aligned year ends makes it easier to calculate and plan around these shared thresholds.
Practical checklist for choosing your year end
- Does it align with your personal tax planning? A 31 March year end gives you the most flexibility to plan salary and dividends before the personal tax year closes.
- Does it avoid your busiest operational period? Preparing accounts during peak season is stressful and error-prone.
- Does it give you cash flow breathing room? A later year end defers your Corporation Tax payment date.
- Does it suit your accountant’s schedule? Off-peak year ends may mean faster turnaround and lower fees.
- Does it align with any group or parent company? Consistency across related companies avoids complications.
The year-end date is one of those decisions that gets made once and then affects your business every year. It is worth spending time to get it right rather than accepting the default.