Do I need to file a CT600 for a dormant company?

By Ben Davies · Updated 5 October 2026

Not every dormant company needs to file a CT600 with HMRC. Whether you need to depends on one question: has HMRC sent the company a notice to deliver a Company Tax Return? (That notice is HMRC's formal letter asking for the return, form CT603.)

Our free Am I dormant? checker gives you a direct answer for both HMRC and Companies House in eight questions, which is the simplest way to find out where you stand.

The decision tree

Has HMRC sent a notice to deliver a Company Tax Return for the period?
├── YES → File a CT600 for the period it names (plus annual accounts)
└── NO  → You only need to file annual accounts with Companies House

A Company Tax Return is legally due when HMRC sends a notice to deliver one. HMRC can send one every year, even to a dormant company. If a notice arrives, you file a nil CT600 for the period it names — even if the company was dormant all year. If no notice arrives, no return is due.

If you do need to file, the complete CT600 guide for dormant companies walks through the whole process.

How to tell whether HMRC will ask

HMRC doesn't publish a company's tax record, so the notice itself is the only sure sign. Every new company gets a Corporation Tax record soon after incorporation, and many dormant companies receive a notice to deliver a return every year — companies that never traded as well as companies that used to.

A UTR doesn't settle the question either way. Every company gets a Unique Taxpayer Reference (UTR) after incorporation — a 10-digit number HMRC sends on a letter called a CT41G, not in the notice to deliver. So having a UTR doesn't mean a return is due, and not being able to find one doesn't mean there is nothing to do.

If you think a notice may have gone astray — to an old registered office, say — HMRC's Corporation Tax helpline on 0300 200 3410 can tell you whether one has been issued.

Common scenarios

"We incorporated the company but never traded"

HMRC set up a Corporation Tax record for the company after incorporation. You may well get a notice to deliver a return each year; answer each one with a nil CT600. In a year with no notice, you only file annual accounts with Companies House.

"The company used to trade but is now dormant"

HMRC already knows the company from its trading years, so expect notices to keep coming. Answer every notice you get — with a nil CT600 for a dormant period. No notice means no return for that period.

"We told HMRC the company is dormant"

If a notice to deliver a return still arrives, it must be answered, even for a period when the company was dormant: file a nil CT600 for the period it names. With no notice, there is no return to file. See our guide on how to file a nil CT600.

What all dormant companies need

Whether or not HMRC asks for a tax return, every dormant company must file:

• Annual accounts with Companies House (due 9 months after your accounting reference date)
• Confirmation statement (CS01) with Companies House (due at least once every 12 months, £50 online / £110 paper)

We cover the full process in our guide on how to file dormant company accounts.

How DormantFile helps

If you do need both filings, DormantFile files dormant accounts and nil CT600 returns from one dashboard, and reminds you when the confirmation statement is due (you file that one yourself). We work only with dormant and non-trading companies — if your company is trading, or its return would show a profit or tax to pay, you need an accountant. Plans start at £19/year.

Key points

• You only need a CT600 when HMRC sends the company a notice to deliver one.
• A notice, once sent, must be answered, even for a dormant period.
• A UTR doesn't tell you either way: every company gets one after incorporation, on HMRC's CT41G letter.
• If you think a notice went astray, HMRC's helpline (0300 200 3410) can tell you whether one was issued.
• All dormant companies need annual accounts with Companies House, whether or not HMRC asks for a return.