Companies House Accounts Deadline: When Are Your Accounts Due?

If you run or look after the books of a UK limited company, the date your annual accounts are due at Companies House is one of the dates you cannot afford to get wrong. The rule is simple, but it works differently for a company's first accounts, and that is where mistakes happen.

The two rules in one minute

According to GOV.UK, a private limited company must file its accounts with Companies House by:

• First accounts: 21 months after the date the company was registered with Companies House.
• Every set after that: 9 months after the end of the company's financial year.

The Corporation Tax return and payment go to HMRC, not Companies House, and have different deadlines (see below).

Worked example: a later set of accounts

A company's financial year ends on 31 March 2026. Nine months after that is 31 December 2026. That is the Companies House deadline for those accounts.

The date moves with the year end. A 30 June year end gives 31 March the next year. Always count months on the calendar, not 30-day blocks, because months have different lengths.

Worked example: first accounts

A company is registered with Companies House on 10 May 2026. Twenty-one months after that is 10 February 2028, which is the date GOV.UK's wording points to for the first accounts.

This is why you should not apply the "9 months after year end" rule to a brand-new company. The first accounts follow a different rule and the date is usually later than people expect. Check how your client's date is calculated before you put it in the diary.

Companies House and HMRC are separate deadlines

Filing accounts at Companies House does not file the tax return. GOV.UK sets out the HMRC dates as:

• Corporation Tax payment: 9 months and 1 day after the accounting period ends. This is also the deadline to tell HMRC if no tax is owed.
• Company Tax Return: 12 months after the accounting period ends.

So a company with a 31 March 2026 year end pays Corporation Tax by 1 January 2027 and files the Company Tax Return by 31 March 2027, but its Companies House accounts are due by 31 December 2026. Three dates, two organisations.

What happens if you are late

Companies House charges an automatic penalty for late accounts. For a private company, GOV.UK lists £150 if the accounts are up to one month late, rising to £1,500 if they are more than six months late, and the penalty doubles if accounts are late two years in a row. See our guide to late filing penalties for the full scale.

Common mistakes

1. Using 30-day maths. "270 days after year end" lands on the wrong day. Use calendar months.
2. Treating first accounts like later accounts. The first deadline is counted from registration, not year end.
3. Assuming a changed year end changes nothing. If the accounting reference date changes, the deadline moves too.
4. Mixing up Companies House and HMRC dates. They are different filings with different deadlines.
5. Relying on a reminder from the client. The company, not the accountant, is responsible, but your practice usually carries the diary.

How to keep track across many clients

A spreadsheet works until it does not: a missed row, a changed year end, a company that was registered mid-month. Whatever system you use, each date should record the rule it came from, so anyone in the practice can check it.

That is the principle behind FilingKeeper, a deadline tracker for small UK accounting and bookkeeping practices. It works out Companies House and HMRC dates from the published GOV.UK rules and shows the rule behind each one. It is in beta, and it does not file anything for you.

Want a free check? Email up to 10 company numbers to haseeb@filingkeeper.com and you will get each client's deadlines back within 24 hours, with the GOV.UK rule behind every date.