How to Register for Corporation Tax

If you have recently set up a limited company and started trading, you must register with HMRC for corporation tax. Every UK limited company that becomes active must notify HMRC within 3 months of starting business, even if you expect to make a loss or owe no tax.

This guide explains who must register, when to do it, how to complete registration online step by step, and what to expect afterwards.

Who Needs to Register for Corporation Tax?

You must register for corporation tax if your company is:

• A UK limited company that has started trading or receiving income
• A foreign company with a UK branch or office
• An unincorporated association, club, or co-operative that has become active

HMRC considers your company active if you are doing any of the following:

• Buying or selling goods or services
• Advertising your business
• Renting out property
• Receiving income from investments
• Employing people

If your company is genuinely dormant — not trading, not receiving income, and not making significant transactions — you do not need to register immediately. See our guide to dormant company tax returns for details on when a company qualifies as dormant.

Note that dormant status for HMRC purposes is determined separately from Companies House. A company can be dormant for HMRC even if it is registered as active at Companies House.

When Is the Deadline?

You must notify HMRC within 3 months of the start of your accounting period — which typically begins on the date your company first starts doing business.

Example:

• Companies House incorporation date: 1 February 2025
• Date trading starts: 1 April 2025
• Corporation tax registration deadline: 1 July 2025 (3 months from 1 April)

Do not confuse your incorporation date with the start of trading. Your registration deadline runs from when you actually begin business activity, not from when Companies House registered your company.

If you miss the 3-month deadline, HMRC may issue a penalty for failure to notify. Register as early as possible once you start trading.

What You Need Before Registering

Gather the following information before starting:

Information needed	Where to find it
Company Registration Number (CRN)	Certificate of incorporation from Companies House
Date you started doing business	Your own records
Date your first accounts are made up to	Typically 12 months after incorporation date
Your company's 10-digit UTR	HMRC welcome letter sent to registered office
Registered office address	Companies House records

Your Unique Taxpayer Reference (UTR) is a 10-digit number that HMRC sends to your registered office within 15 working days of Companies House incorporation. You will need it to enrol for corporation tax online. For more on UTR numbers and how to find them, see our UTR number explained guide.

How to Register Online

The fastest way to register is through your HMRC business tax account.

Step 1: Set Up a Government Gateway Account

If you do not already have a Government Gateway account for your company, visit gov.uk/log-in-register-hmrc-online-services and create a business tax account:

1. Select "Create sign-in details"
2. Choose "Organisation" as the account type
3. Provide your company's name and registration number

Step 2: Enrol for Corporation Tax

Once signed in to your business tax account:

1. Select "Services you can add" in the left-hand menu
2. Find "Corporation Tax" and select "Enrol for service"
3. Enter your 10-digit UTR when prompted
4. Enter your company's accounting period start date and accounts end date

Step 3: Verify Your Registered Office Address

Before completing enrolment, confirm that your registered office address at Companies House is correct. HMRC sends all future correspondence — including the activation code and payment reminders — to this address.

Step 4: Wait for the Activation Code

After enrolling, HMRC posts an activation code to your registered office. This typically arrives within:

• 10 working days for UK addresses
• 21 working days for overseas addresses

If you do not receive the activation code, you can request a replacement through your business tax account.

Step 5: Activate Your Account

Log back in to your business tax account and enter the activation code when prompted. Your company is now fully registered for corporation tax and can file returns and make payments online.

How to Register by Post

If you are unable to register online, you can write to HMRC at:

Corporation Tax Services HM Revenue and Customs BX9 1AX United Kingdom

Your letter must be signed by a director or company secretary and include:

• Company name and Companies House registration number
• Date trading started (accounting period start date)
• Date your first accounts are made up to
• Principal place of business
• Nature of business
• Names and home addresses of all directors
• Details of any parent company (if applicable)

Postal registration is slower. Online registration is recommended for most companies.

What Happens After Registration?

Once your company is registered for corporation tax, HMRC will:

1. Confirm your registration by sending a letter to your registered office
2. Provide your corporation tax payment deadline
3. Issue a notice requiring you to file a Company Tax Return (CT600) for each accounting period

You must then:

• File your company tax return within 12 months of the end of each accounting period
• Pay corporation tax owed within 9 months and 1 day of the end of your accounting period
• File a return even if you make a loss or owe no tax — the obligation to file exists regardless of your profit position

For a full breakdown of key dates, see our guide to company tax return deadlines.

Do You Need an Accountant to Register?

No. Registering for corporation tax is a straightforward process that most directors can complete themselves via the HMRC business tax account. The main requirements are having your UTR and knowing your accounting period start and end dates.

However, if you are unsure about your accounting period dates, or if your company's situation is complex (for example, you have associated companies or are part of a group), professional advice may be worthwhile.

If you are planning to file your own corporation tax return once registered, see our guide on your first company tax return for what to expect.

What If Your Company Becomes Dormant?

If your company later ceases trading or becomes dormant, you should inform HMRC. You can do this through your business tax account or by writing to the Corporation Tax office. HMRC may then agree that the company does not need to file returns while dormant.

See our dormant company CT600 guide for the full process.

Penalties for Not Registering

Failure to notify HMRC of a new tax obligation is known as "failure to notify" and can result in a penalty. The amount depends on how late you are and whether the failure was deliberate.

In addition, once your accounting period has ended, you face separate late filing penalties if your company tax return is not filed on time — starting at £100 and increasing the longer the return remains outstanding. For details, see our guide to corporation tax penalties.

Summary

Every UK limited company must register with HMRC for corporation tax within 3 months of becoming active. The fastest way is through your HMRC business tax account using your company registration number and UTR. After enrolling, HMRC posts an activation code to your registered office — enter it to complete registration. Once registered, you must file a company tax return within 12 months of your accounting period end and pay any corporation tax owed within 9 months and 1 day, regardless of whether you make a profit.