UK private limited companies must file annual accounts with Companies House within 9 months of the accounting period end. Public companies have 6 months. First accounts (after incorporation) are due either 21 months after incorporation OR 3 months after the first accounting reference date, whichever is later. Late accounts trigger automatic penalties from £150 to £1,500 for private companies.

This is the most common UK SME deadline failure. Accounts are usually delegated to an accountant. The deadline still belongs to the director.

The basic rule

For private limited companies (Ltd) and LLPs:

9 months after the accounting period end to file at Companies House.

For public limited companies (PLC):

6 months after the accounting period end.

The "accounting period" is the period the accounts cover. The accounting reference date (ARD) is the last day of the accounting period — typically the anniversary of incorporation (set at month-end by default, e.g. a company incorporated 12 March has an ARD of 31 March).

First accounts — the special rule

The first accounts after incorporation cover a longer period (the partial first year). The deadline is:

21 months after incorporation date, OR
3 months after the first accounting reference date,
whichever is later.

Example: company incorporated 12 March 2025, ARD 31 March (so the first accounting period runs from 12 March 2025 to 31 March 2026, 12 months and 19 days).

21 months after incorporation: 12 December 2026.
3 months after ARD: 30 June 2026.
First accounts deadline: 12 December 2026 (the later date).

Subsequent years follow the normal 9-month rule.

What gets filed

Depends on company size — different reporting requirements for:

Micro-entity

Turnover ≤ £632,000.
Balance sheet total ≤ £316,000.
Average employees ≤ 10.
Very abbreviated balance sheet + footnotes only.

Small company

Turnover ≤ £10.2m.
Balance sheet total ≤ £5.1m.
Average employees ≤ 50.
Abbreviated accounts (less detail than full).

Medium-sized

Turnover ≤ £36m.
Balance sheet total ≤ £18m.
Average employees ≤ 250.
Slightly fewer disclosures than full accounts.

Large

Above all three criteria.
Full statutory accounts with all required disclosures.

To qualify as a smaller category, the company must meet at least 2 of the 3 criteria for 2 consecutive years.

Most UK SMEs file micro-entity or small company accounts.

Late filing penalties (private companies)

How late	Penalty
Up to 1 month	£150
1-3 months	£375
3-6 months	£750
Over 6 months	£1,500

For public companies, penalties are 5× higher.

Critical: penalties double if accounts are filed late two years in a row. So missing the second consecutive year by 6+ months is a £3,000 penalty.

Penalties are paid by the company (NOT the director personally), within 28 days of the penalty notice.

Reasonable excuse appeals

Late filing penalties can be appealed if there''s a "reasonable excuse". The bar is narrow — typically:

Serious illness or bereavement of the person responsible.
Fire, flood, or disaster destroying records.
Companies House system outage on the day.

Not accepted as reasonable excuse:

"Accountant was late."
"We were waiting on missing information."
"We forgot."
"Companies House didn''t remind us."

The reasonable-excuse test is more like Self Assessment''s than wider tribunal standards — narrow and rigid.

How to file

Filing methods for UK accounts:

Companies House WebFiling

Online portal.
Free.
Most appropriate for small / micro-entity accounts that fit a standard template.

Accounting software with Companies House integration

Xero, QuickBooks, Sage Business Cloud, FreeAgent all support direct filing.
Pre-fills the accounts from your accounting data.
Better for slightly more complex small / medium accounts.

Paper filing

Still permitted but penalised. Submit form AA (private companies, small) or AA02 (public).
Discouraged. Slower processing, higher risk of rejection.

Filed by accountant via their accountant API

Most SMEs use their accountant. The accountant prepares and files using HMRC-recognised accounts production software.

The relationship with Corporation Tax

Two separate filings:

Accounts to Companies House (this article): public filing, format follows Companies Act 2006.
CT600 to HMRC: tax return, includes detailed tax computation.

Both must be done. The accounts feed into the CT600, but they''re filed in different places to different government bodies with different deadlines.

Common mistakes

Confusing CT and Companies House deadlines

Accounts to Companies House: 9 months after period end.
CT600 to HMRC: 12 months after period end.
CT payment to HMRC: 9 months and 1 day after period end.

These are all different. Track separately.

Confirm your company''s accounting reference date on Companies House.
Note the filing deadline (9 months from ARD).
Set calendar reminders at 60, 30, and 7 days before the deadline.
If you use an accountant, confirm in writing they''re filing accounts AND CT600, not just one.
Submit accounts before Christmas for January deadlines. Last-minute filing has the highest risk of system issues.

Annual accounts filing: when and how