Missing a Companies House accounts deadline is one of the most visible mistakes a practice can make. The penalty lands on the client, the register shows the company as overdue for anyone to see, and the conversation that follows is rarely a comfortable one. The rules themselves are simple. The difficulty is applying them across dozens or hundreds of companies, each with its own year end.
The basic rule
A private limited company must file its annual accounts at Companies House within 9 months of the end of its accounting reference period. For a company with a 31 March year end, the deadline is 31 December. For a 30 June year end, it is 31 March the following year.
Where the year end falls on the last day of a month, the deadline is the last day of the month nine months later. So a 28 February year end has a 30 November deadline, not 28 November.
Public companies have 6 months, but most clients of small practices will be private companies.
First accounts
A new company’s first accounts are different. If the first accounting period is longer than 12 months, the accounts are due 21 months after the date of incorporation, or 3 months after the accounting reference date, whichever is later. A company incorporated on 14 March 2025 with its first accounts made up to 31 March 2026 must file by 14 December 2026.
This is the deadline most often missed for newly formed clients, because nobody expects the first filing to be due so long after incorporation, and it is easy to lose track of it.
When the year end changes
A company can shorten its accounting reference period as often as it likes, and extend it once every five years (with some exceptions). Shortening the period can bring the filing deadline forward: the new deadline is the later of 9 months after the new year end and 3 months from the date the change was filed.
If you change a client’s year end, update your records the same day. In Deadlio, use the Next period end – override field so that the accounts, Corporation Tax payment and CT600 dates all move together, and clear it once the accounts are filed.
Late filing penalties
Penalties for private companies depend on how late the accounts are:
- up to 1 month late: £150
- 1 to 3 months: £375
- 3 to 6 months: £750
- more than 6 months: £1,500
The penalty is doubled if the accounts were also filed late the previous year. Directors can also be prosecuted, and persistent failure can lead to the company being struck off the register.
Companies House will only consider an appeal in exceptional circumstances. “The accountant was busy” is not one of them.
How Companies House shows the deadline
Every company’s page on the Companies House register shows “Next accounts made up to … due by …”. This is the most reliable source for the next deadline because it already reflects any change of year end. If that date ever disagrees with your own records, find out why before the deadline arrives.
Deadlio reads these dates from the public register every day, so when a client files – or when someone changes the year end without telling you – the register and your deadlines stay in step.
Practical tips for practices
- Record the year end you actually filed, not the date you filed it. In Deadlio this is Last accounts made up to. It drives the next period end and the tax deadlines.
- Watch dormant and small clients. They are quick to prepare, so they tend to be left until last.
- Allow time for director approval. The filing deadline is the date Companies House must receive the accounts, so build in time for the client to review and sign.
- Look at the whole picture. Accounts, the confirmation statement and the Corporation Tax deadlines all depend on the same dates. A single view of all of them avoids surprises.
Related guides
- Confirmation statement deadline
- Corporation Tax payment deadline
- CT600 return filing deadline
- Charity Commission annual return
- See it in practice: The £375 surprise: how a new company’s first accounts slipped through
- See it in practice: The year-end change nobody diarised
- All deadline guides
Track every client’s accounts deadline automatically. Deadlio reads Companies House dates for each client and shows what is overdue, due this week and due this month. Start a free 30-day trial – no card needed.
This guide is general information for accountancy practices and is not a substitute for checking the current rules on GOV.UK. Last reviewed October 2026.