CT600 for dormant & non-trading companies
Every UK limited company has to deal with the Company Tax Return (form CT600) at some point — and dormant and non-trading companies have specific rules that catch most directors out. Neither has tax to pay; what changes is the accounts you attach. CICs, LLPs and guarantee companies each reach the return by a different route — there's a section for them below. This is the complete reference: guides, plain-English answers, and free tools, organised so you can find what you need.
Start here
The two pieces every dormant-company director should read before doing anything else with HMRC.
Guide
The complete guide to filing a CT600 for a dormant company
The long-form reference. Covers when you owe a CT600, the nil-return process, pitfalls, and what to do if you're years behind.
Tool
Do I need to file a Company Tax Return? — free CT600 checker
Answer 7 questions and we'll tell you exactly which CT600 you owe (nil, full, or none) and what to do.
Understanding the obligation
What a CT600 is, when it applies, and how HMRC's notice system works.
Answer
What is a CT600?
Plain-English explanation of the Company Tax Return.
Guide
Do I need a CT600 for a dormant company?
The most-asked question about dormant CT600s — and why the answer turns on whether HMRC has sent a notice to deliver one.
Guide
Non-trading company with a Bounce Back Loan
When the company isn't dormant but still has no tax to pay — file micro-entity accounts alongside the CT600.
Answer
What are micro-entity accounts (FRS 105)?
The accounts a non-trading company attaches instead of dormant ones — there's still no tax to pay.
Answer
What is a UTR number?
Your company's Unique Taxpayer Reference, and why you need it before filing a CT600.
Answer
What is the HMRC Gateway?
The HMRC login you need to file a CT600 electronically.
Not an ordinary limited company?
A CIC, an LLP or a company limited by guarantee each meets the Company Tax Return differently — and for two of them the return isn't a CT600 at all.
Answer
Does DormantFile support CIC companies?
Yes for the Company Tax Return — a CIC's nil CT600 files like any other company's. No for the accounts, which need a CIC34 report and £15 fee no software can send.
Guide
How to file CIC accounts — including for a dormant CIC
The other half of a CIC's year: the CIC34 report, the £15 fee, the routes Companies House accepts, and how the CT600 fits alongside them.
Answer
Can a CIC be dormant?
A CIC can be dormant for Corporation Tax — but it keeps the CIC34 and the £15 fee, and the CIC Regulator won't let it sit dormant forever.
Answer
Does a dormant LLP need to file a tax return?
An LLP is taxed as a partnership, so the return it can owe is the Partnership Tax Return (SA800) rather than a Company Tax Return (CT600) — due only for years HMRC issues a notice to file.
Answer
Does a flat management company need a CT600?
Guarantee companies are within Corporation Tax scope — when a flat management company owes a nil CT600, and what HMRC's letters mean.
Filing a nil CT600
The practical steps for a nil CT600 (a return showing no tax due) — and the gotchas that catch directors out.
Guide
How to file a nil CT600 tax return with HMRC
What a nil CT600 contains, why it now needs commercial software, and how DormantFile files it for you.
Guide
How CT600 filing works in DormantFile
A walkthrough of the Corporation Tax section: adding periods, attaching accounts, signing with your Government Gateway, and getting confirmation.
Guide
How to get proof of dormant company filing
Which confirmations prove you filed — the submission reference, IRmark and correlation ID — and where to find them.
Answer
What is a filing receipt?
What HMRC's acceptance response actually contains.
Penalties and overdue returns
If you're behind on CT600s, the penalty exposure and how to recover.
Guide
Late filing penalties for dormant companies
The full breakdown of HMRC and Companies House penalty bands for missed filings.
Guide
HMRC penalty letters explained
Reference guide to every HMRC letter you might receive — the notice to file a return (CT603), penalty notices, the letter with your UTR (CT41G) — and what to do.
Guide
Catching up on overdue dormant company filings
Practical playbook if you're multiple years behind on accounts or CT600 returns.
Guide
HMRC letter about your dormant company: what to do
The calm-down response if you've just opened an HMRC letter.
Tool
What is this letter? — free letter reader
Photograph the letter and find out what it is, what it costs, and when it's due — no signup needed.
Deadlines and dates
When CT600s are due, and how to keep on top of yours.
Guide
Dormant company filing deadlines explained
Accounts, Company Tax Return (CT600), and confirmation statement deadlines — when they fall and how they relate.
Tool
Dormant deadline calculator
Enter your incorporation date and we'll tell you the next three deadlines you owe.
Guide
How to add filing deadlines to your calendar
Subscribe to a personal iCal feed so your deadlines — including CT600 dates for the periods you've added — appear in Google or Apple Calendar.
Not sure what your dormant or non-trading company needs to file?
Find your company and we'll show you its deadlines and what we can file for it. Free, and no account needed.
Check my company →Not ready to file? Get the free deadline watchdog — Companies House deadline reminders, strike-off alerts and register watch, no card needed.