Registering for Corporation Tax

Key facts

Companies House notifies HMRC when a company is incorporated, but you must still register for CT when the company becomes active.
You have 3 months from the date the company starts trading or receiving income to register.
Registration can be done online or via form CT41G.
HMRC will issue a 10-digit UTR (Unique Taxpayer Reference) for the company.

Who Must Register?

Any UK limited company that is active must register for Corporation Tax. “Active” means the company has done any of the following:^[1]

Started carrying on a business or trade
Received any taxable income (e.g. bank interest, rental income)
Bought or sold any chargeable assets

If the company is dormant (it has never traded and has no income), you do not need to register for Corporation Tax. However, HMRC may still contact you after incorporation to ask about the company’s status.

How to Register

There are two ways to register:^[1]

Option 1: Register Online (Recommended)

Use HMRC’s online service at gov.uk. You will need:

The company’s registered number (from the Certificate of Incorporation)
The date of incorporation
The date the company started being active
The company’s registered office address
The nature of the business (SIC code)
The accounting period end date (financial year end)
Details of any directors and company secretary

Option 2: Form CT41G

HMRC usually posts a CT41G form to the company’s registered office shortly after incorporation. You complete and return it with the same information as above. Processing takes longer than online registration.^[2]

Tip: Register online as soon as the company becomes active — don’t wait for the CT41G letter to arrive. Online registration is faster and ensures you meet the 3-month deadline.^[1]

Your Company UTR

After registration, HMRC will send the company a Unique Taxpayer Reference (UTR) — a 10-digit number. This is used for:^[3]

Filing your CT600 Company Tax Return
Making Corporation Tax payments to HMRC
All written correspondence with HMRC about the company’s tax affairs

The company UTR is different from any personal UTR that a director may have for their individual Self Assessment. Keep them separate to avoid payment allocation errors.

How long does it take? After registering online, most companies receive their UTR by post within 7–14 working days. You can also find it in your HMRC online services once your Business Tax Account is set up.^[1]

What Happens After Registration

Once registered, HMRC will:^[4]

Set up the company for Corporation Tax and issue the UTR
Send a “notice to deliver” a Company Tax Return (CT600) after the end of the first accounting period
Expect a CT600 return within 12 months of the end of each accounting period
Expect Corporation Tax payment within 9 months and 1 day of the end of each accounting period

Even if HMRC does not send a “notice to deliver,” you are still legally required to file a CT600 and pay any tax due. Not receiving a notice is not a defence against late filing penalties.

What If You Register Late?

There is no specific penalty for registering for Corporation Tax late. However, late registration often leads to:

Late filing penalties — if you miss the CT600 deadline because you were unaware of it
Late payment interest — if Corporation Tax is not paid on time
Estimated assessments — HMRC may issue a “determination” estimating your tax (often high) if no return is filed

Frequently Asked Questions

How do I register my company for Corporation Tax?

Register online through HMRC’s service at gov.uk using your company’s registered number and incorporation date. Alternatively, complete form CT41G, which HMRC may send to your registered office after incorporation.

How long do I have to register for Corporation Tax?

You must register within 3 months of the company becoming active — that is, starting to trade, receiving taxable income, or buying and selling assets.

What is a company UTR number?

The Unique Taxpayer Reference is a 10-digit number issued by HMRC after you register for Corporation Tax. It is used for filing CT600 returns, making tax payments, and all correspondence with HMRC.

Do dormant companies need to register for Corporation Tax?

No. If your company has never traded and has no income, you do not need to register. However, HMRC may contact you after incorporation to confirm the company’s status.

Sources

Register for Corporation Tax — GOV.UK
Set up your company for Corporation Tax — GOV.UK
Corporation Tax — GOV.UK
Company Tax Returns — GOV.UK