To file a Company Tax Return for a dormant company, submit a CT600 online with zeros in the income, expenditure, and tax fields, using commercial software, by the deadline 12 months after the end of your accounting period. You only need to do this if HMRC has sent you a notice to deliver a Company Tax Return. Once you’ve filed that return, you can formally tell HMRC the company is dormant and stop filing CT600s until it starts trading again.
Do You Actually Need to File a CT600?
The trigger is the notice. If HMRC has sent you a “notice to deliver a Company Tax Return,” you are required to file a CT600 online for that period, even if the company did nothing during it.1GOV.UK. Dormant for Corporation Tax The return shows HMRC the company was dormant across that accounting period, with zero turnover, zero profit, and zero tax due.
If HMRC has not sent a notice, and you’ve already told them the company is dormant, you don’t need to file. The obligation only kicks back in if HMRC asks for a return or the company starts trading again.2GOV.UK. Tell HMRC Your Company Is Dormant for Corporation Tax
One point that trips people up: HMRC’s definition of dormant is stricter than the Companies House one. For Corporation Tax purposes, dormant means no trading and no other income of any kind, including bank interest. Buying, selling, renting property, advertising, employing anyone, and earning interest all count as trading.1GOV.UK. Dormant for Corporation Tax If your “dormant” company earned even a few pounds of interest, it isn’t dormant for HMRC, and a nil return would be wrong.
The Filing Deadline
The CT600 is due 12 months after the end of your company’s accounting period. Corporation Tax, if any were owed, would be due earlier, at 9 months and 1 day after the accounting period ends. For a genuinely dormant company the tax owed is zero, but the 12-month filing deadline still applies, and missing it triggers penalties.
What You Need Before You Start
Gather these before you sit down to file:
- Your Unique Taxpayer Reference (UTR): a 10-digit number HMRC issued when the company registered for Corporation Tax. It’s on earlier HMRC correspondence and previous returns.3HM Revenue & Customs. Completing Your Company Tax Return
- Your company registration number: the 8-digit number Companies House assigned at incorporation.
- Government Gateway credentials: a user ID (up to 12 characters) and password for HMRC’s online services. If you’ve never signed in, you’ll need to create an account and enrol for Corporation Tax online.4GOV.UK. HMRC Online Services: Sign In or Set Up an Account
Start the Gateway enrolment early. Activation codes for the Corporation Tax service are sent by post to the company’s registered office and can take up to 10 working days to arrive. Leaving this to the last week is a common route to a late filing penalty.
Submitting the Nil CT600 Online
CT600 returns must be filed online, and HMRC does not provide its own filing interface for Corporation Tax. You need to use commercial software. Several providers offer free packages for dormant or simple returns, and HMRC publishes a list of approved suppliers on GOV.UK.5GOV.UK. Corporation Tax Commercial Software Suppliers
The process for a dormant company is straightforward. Select the accounting period. Confirm no trading activity occurred. Enter zero in the income, expenditure, and tax fields. If accounts must accompany the return, file a simple balance sheet showing no change from the prior period. Review the summary screens, then transmit the return.
After a successful submission, you’ll get an on-screen acknowledgment and a confirmation from HMRC. Save it. It’s your evidence of on-time filing if HMRC ever queries the return.
Tell HMRC the Company Is Dormant So Returns Stop
Filing the CT600 clears the notice HMRC already sent. It doesn’t stop them sending another one next year. To close the loop, use HMRC’s online service to formally declare the company dormant for Corporation Tax. You can also do this by phone or post. Once HMRC acknowledges the dormancy, you won’t have to file another Company Tax Return unless HMRC asks you to or the company begins trading again.2GOV.UK. Tell HMRC Your Company Is Dormant for Corporation Tax
Do this step. It’s the piece most owners of dormant companies miss, and it’s the difference between one final nil return and filing one every year indefinitely.
Companies House Is a Separate Filing
Telling HMRC the company is dormant does not excuse you from Companies House. You must still file annual accounts and a confirmation statement every year.6GOV.UK. Dormant for Companies House
For a company that has never traded and whose only transaction was issuing subscriber shares on incorporation, you can file dormant accounts using the AA02 form.7GOV.UK. File Your Dormant Accounts (AA02) Companies that previously traded but have since gone dormant will file abbreviated or micro-entity accounts showing a static balance sheet. The deadline for a private company’s annual accounts is 9 months after the end of the accounting reference date. The confirmation statement is separate and confirms basic details such as the registered address, directors, and shareholders. Missing either puts the company at risk of being struck off the register.
Late Filing Penalties
Penalties come from two directions, and they run independently.
HMRC Penalties for a Late CT600
For accounting periods starting on or after 1 April 2026, the penalties are:8HM Revenue & Customs. Corporation Tax: Penalty Determinations (CT211 Notes)
- Within 3 months late: £200
- More than 3 months late: £400
- Third successive late return within 3 months: £1,000
- Third successive late return more than 3 months late: £2,000
HMRC can also estimate the tax bill and add a tax-related penalty of up to 10% of unpaid tax at six months, and another 10% at twelve months.9GOV.UK. Company Tax Returns: Penalties for Late Filing For a genuinely dormant company with no tax liability, the percentage penalties don’t apply. The flat-rate ones do.
Companies House Penalties for Late Accounts
Companies House applies its own scale, and it applies to dormant companies:10GOV.UK. Late Filing Penalties
- Up to 1 month late: £150
- 1 to 3 months late: £375
- 3 to 6 months late: £750
- More than 6 months late: £1,500
If accounts are filed late in two successive years, the penalty doubles. A dormant company that falls behind on both HMRC and Companies House filings can pile up more than £1,000 in penalties for what amounts to a nil return.
If the Company Starts Trading Again
When the company starts trading or receiving income again, tell HMRC within three months of the start of your new Corporation Tax accounting period.11GOV.UK. Corporation Tax: Trading and Non-Trading You can do this through the online service. The company then becomes liable for Corporation Tax at 19% on profits up to £50,000 and 25% on profits above £250,000, with a sliding marginal rate in between. Full CT600 returns, statutory accounts, and any payroll obligations resume. The simplified dormant cycle ends.