Do dormant companies need to file a CT600?

By Max Szolcek, founder of Dormant Return. Last updated 21 August 2026

Sometimes. It depends on one thing: whether HMRC has sent your company a notice to deliver a Company Tax Return. If it has, you must file a CT600 even though a dormant company owes no Corporation Tax. If HMRC has agreed the company is dormant and has not sent a notice, no return is due.

The short answer

A Company Tax Return (the CT600 form, together with accounts) is due when HMRC issues a notice to deliver one, usually on form CT603. The obligation comes from the notice, not from whether any tax is owed. HMRC's own guidance is explicit that a penalty for a late return can be charged even if the company owes no Corporation Tax at all.

So the question splits into two situations:

HMRC has sent a notice to deliver a return (or your company has filed returns before and HMRC still expects one): you must file a CT600 for that period, even if the company did nothing.
HMRC has agreed the company is dormant and has not issued a notice: no CT600 is needed until HMRC says otherwise. See how to tell HMRC your company is dormant.

What counts as dormant for Corporation Tax

HMRC treats a company as dormant when it is not active, not trading and has no other income. In gov.uk's words, a company is usually dormant for Corporation Tax if it has stopped trading and has no other income (for example from investments), is a new company that has not started trading, or is one of a few special cases such as a flat management company.

Be careful with the word trading. For HMRC it is broad: buying, selling, renting property, advertising, employing someone or earning interest all count as trading activity. A company with even a few pounds of bank interest in the period is not dormant for Corporation Tax.

Note that dormant means something different at Companies House, which looks at significant accounting transactions rather than trading. A company can be dormant for one regulator and not the other; the two also have entirely separate filings. The differences are covered in dormant for Companies House vs dormant for Corporation Tax.

Why you cannot just ignore it because no tax is due

Late filing penalties are fixed and automatic: £200 the day after the deadline and another £200 three months later, rising to £1,000 each if the return is late three times in a row. None of that depends on tax being owed. For a company whose return is entirely zeroes, the penalties can easily exceed anything the company has ever earned. The full ladder is in late CT600 penalties for dormant companies.

What a dormant company's CT600 actually contains

Very little. The return declares the accounting period and the company's details, reports nil trading income and nil tax, and carries the company's accounts embedded in iXBRL format (a machine-readable tagging of the figures that HMRC requires; see dormant company iXBRL accounts explained). For most dormant companies the accounts are a balance sheet of zeroes with the required declarations.

The difficulty was never the content. It is that since HMRC closed its free online filing service on 31 March 2026, a Company Tax Return can only be filed through commercial software; paper filing is limited to companies with a reasonable excuse or filing in Welsh. The background is in HMRC's free filing service has closed.

Need to file one? Dormant Return prepares your CT600 and dormant accounts and files them straight to HMRC under your own Government Gateway sign-in. It takes about five minutes and costs £5, refunded automatically if HMRC rejects the return.

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If you are not sure whether HMRC expects a return

Check the company's post for a form CT603 notice to deliver a Company Tax Return, or sign in to the company's HMRC business tax account, which lists outstanding Corporation Tax obligations and their deadlines. If nothing is due and the company will stay inactive, telling HMRC the company is dormant usually stops future notices being issued.