What counts as dormant
Your company is dormant for Corporation Tax if it had no significant transactions during the year — no sales, no expenses run through the company, no interest earned on its money.
Dormant does not mean exempt, however. HMRC and Companies House still expect their filings on time, even when every figure is zero, and late filing can still result in a penalty.
Dormant for HMRC is not the same as dormant for Companies House
The two bodies use different definitions, and this catches people out. For HMRC, dormant broadly means the company is not active — no trading and no income. For Companies House, it means no significant accounting transactions went through the books during the year (a small number of items, such as fees paid to Companies House itself, are ignored).
A company can therefore qualify as dormant with one body but not the other. For example, a company that earns a little bank interest may still be filing dormant accounts at Companies House while owing HMRC a return that declares the interest.
The safe approach is to check your position against each definition separately rather than assuming one answer covers both.
What you have to send
A Company Tax Return (the CT600) to HMRC, together with a short tax computation and dormant accounts.
Dormant accounts to Companies House.
You do not need to prepare any of these documents yourself — OneFiler creates all of them from a few simple answers and files them for you.
What to have ready
Your company registration number and your Corporation Tax reference (your UTR).
The Government Gateway login for your company.
The dates your accounting period covers.
When it is due
Your tax return is normally due 12 months after your accounting period ends.
Your dormant accounts are due at Companies House 9 months after the period ends.
Late filing can result in penalties, so it is worth completing everything early — particularly when the filing itself takes only minutes.
Common mistakes to avoid
Assuming dormant means no filings at all. It does not — the returns still have to go in, just with zeros in them.
Letting bank interest accumulate. Even a small amount of interest means the company has income, which can take it out of dormancy for Corporation Tax.
Forgetting the confirmation statement. This is a separate Companies House filing that every company must make at least once a year, dormant or not.
Not telling HMRC the company is dormant. If HMRC has issued a notice to file, you must file a return even if the company did nothing — until HMRC agrees the company is dormant, it will keep expecting returns.