Dormant company filing deadlines explained

By DormantFile · Updated 28 March 2026

Dormant companies have the same filing deadlines as trading companies. Missing them triggers automatic penalties. Here is how the deadlines work.

If you just want the dates, our free dormant deadline calculator works them out for you from your incorporation date or ARD — accounts, CT600, and confirmation statement in one go.

Annual accounts (Companies House)

Annual accounts must be filed within 9 months of the end of your accounting reference period.

Your accounting reference date (ARD) is the date your annual accounts are prepared up to. By default, it is the last day of the month in which the anniversary of your company's incorporation falls.

Example: Company incorporated 15 June 2024. Default ARD = 30 June. First accounting period ends 30 June 2025. Because this first period is longer than 12 months, the first-year rule applies (see below): accounts due by 15 March 2026 — 21 months from incorporation.

CT600 (HMRC)

If your company is registered for Corporation Tax, the CT600 must be filed within 12 months of the end of the accounting period.

Using the same example: the first accounting period runs 15 June 2024 to 30 June 2025 — over 12 months, so HMRC splits it into two returns. The first covers the 12 months to 14 June 2025 (CT600 due by 14 June 2026); the second covers 15–30 June 2025 (CT600 due by 30 June 2026). From the second year on it is one return per period, due 12 months after the period end.

The CT600 deadline is 3 months later than the accounts deadline. Not every dormant company needs a CT600 — see our guide on whether you need to file one.

First-year deadlines

First-year deadlines are slightly different. Your first accounting period usually runs longer than 12 months — from incorporation to the last day of that month a year on — and when it does, the Companies House deadline for first accounts is 21 months from the date of incorporation (or 3 months after the period end, if that is later — it almost never is).

Watch the trap: that lands earlier than the standard "9 months after period end" arithmetic would suggest. We cover this in more detail in our guide on first year filing for a new company.

Example: Company incorporated 1 December 2025. ARD = 31 December. First accounting period runs to 31 December 2026 — 13 months, so the first-accounts rule applies. Accounts deadline = 1 September 2027 (21 months from incorporation), not the 30 September 2027 the 9-month rule would give. Diarise the 21-month date.

The first CT600 follows the standard 12-month rule from the end of the accounting period.

Confirmation statement

Separately from accounts, every company must file a confirmation statement (CS01) with Companies House at least once every 12 months from the date of incorporation (or the last confirmation statement). The filing fee is £50 online or £110 paper. This is not the same as annual accounts — it is a separate requirement.

Calendar summary

How to avoid missing deadlines

• We calculate your accounts deadline automatically in DormantFile and send email reminders at 90, 30, 14, 7, 3, and 1 day before it is due. CT600 periods are entered by you — once added, their statutory deadlines are reminded too (HMRC's letter is always definitive).
• You can also check your deadlines on the Companies House company page by searching for your company.
• File early — there is no penalty for filing before the deadline, and both filings can be submitted well in advance.

Key points

• Accounts: 9 months after accounting period end (21 months from incorporation for first accounts).
• CT600: 12 months after accounting period end.
• Confirmation statement: every 12 months, £50 online / £110 paper, separate from accounts.
• Late filing triggers automatic penalties from both Companies House and HMRC. If you're already late, the penalty calculator shows what you owe.