CT600 for dormant & non-trading companies
Every UK limited company has to deal with the Company Tax Return at some point — and dormant and non-trading companies have specific rules that catch most directors out. The tax return is nil in both cases; what changes is the accounts you attach. 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 owe a CT600? — free 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 is almost always yes.
Guide
Non-trading company with a Bounce Back Loan
When the company isn't dormant but the CT600 is still nil — file micro-entity accounts alongside it.
Answer
What are micro-entity accounts (FRS 105)?
The accounts a non-trading company attaches instead of dormant ones — the CT600 stays nil.
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.
Filing a nil CT600
The practical steps — and the gotchas that catch directors out.
Guide
How to file a nil CT600 tax return with HMRC
Step-by-step process with the 6 stages every nil CT600 goes through.
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
The IRmark, correlation ID, and submission reference — what to keep 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 — CT603, CT211, CT204 — 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.
Deadlines and dates
When CT600s are due, and how to never miss one again.
Guide
Dormant company filing deadlines explained
Accounts, 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 deadlines appear in Google or Apple Calendar.
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