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

By DormantFile · Updated 28 March 2026

Not every dormant company needs to file a CT600 with HMRC. Whether you need to depends on one question: is your company registered for Corporation Tax?

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

Is your company registered for Corporation Tax?
├── YES → You need to file a CT600 every year (plus annual accounts)
└── NO  → You only need to file annual accounts with Companies House

If your company is registered for Corporation Tax, you file a nil CT600. If it is not, you do not.

How to tell if you are registered

Your company is registered for Corporation Tax if:

HMRC sent you a Unique Taxpayer Reference (UTR) — a 10-digit number, usually in a letter titled "Notice to deliver a Company Tax Return."
You (or a previous director, or your accountant) notified HMRC that the company was active and needed to register.
The company traded at some point in the past and was registered then.

Your company is probably not registered if:

It was incorporated but never traded.
You never notified HMRC that the company was active.
You never received a UTR from HMRC.

If you are unsure, you can call HMRC's Corporation Tax helpline on 0300 200 3410 to check.

Common scenarios

"We incorporated the company but never traded"

If you formed a company and never did anything with it, you may not have been automatically registered for Corporation Tax. Check whether you have a UTR. If you do not, you likely only need to file annual accounts with Companies House.

"The company used to trade but is now dormant"

If the company was previously trading, it is almost certainly registered for Corporation Tax. You need to continue filing nil CT600 returns unless you formally tell HMRC the company is dormant. Even then, HMRC may still require returns.

"We told HMRC the company is dormant"

You can notify HMRC that your company is dormant. In some cases, HMRC will mark the company as dormant and stop issuing notices to file. But this does not always happen — HMRC may still require CT600 returns. The safest approach is to file unless HMRC explicitly confirms you do not need to. See our guide on how to file a nil CT600.

What all dormant companies need

Regardless of Corporation Tax status, 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, £34 online / £62 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 handles dormant accounts and nil CT600 returns from one dashboard. We deal with dormant company filings only — if your company has traded or has transactions to report, you need accounting software or a professional. Plans start at £19/year.

Key points

You only need a CT600 if your company is registered for Corporation Tax.
Check if you have a UTR — that is the clearest indicator.
If unsure, call HMRC on 0300 200 3410.
All dormant companies need annual accounts with Companies House, regardless of CT status.