How to set up your Company for Corporation Tax in the UK

7 August 2026

When you incorporate a new private limited company, your business details are automatically shared by Companies House with HM Revenue and Customs (HMRC).

You must manually register your business for Corporation Tax and set up your online Government Gateway tax account within three months of commencing to trade.

Failing to register on time can result in financial penalties being issued to the company.

The steps below are required to get your company fully compliant for UK corporate taxes.

Your Unique Taxpayer Reference (UTR)

Before you can register online, you need your company’s unique tax identifier, which is sent by HMRC to the Registered Office of the new company.  The UTR is a ten-digit reference that will be required whenever corresponding with HMRC.

Create an HMRC Business Tax Account

Your personal Government Gateway account cannot be used for corporate taxes, and you must therefore create a dedicated account for your company.

This is how to set up your corporate Government Gateway account:

• Go to the official HMRC sign-in page on GOV.UK.
• Click “Create sign-in details” under the login box.
• Enter your business email address and verify it with the confirmation code sent to you.
• Set up your name, a secure password, and recovery questions.
• Crucial Step: When prompted to choose an account type, select “Organisation”.
• Note down your new 12-digit Government Gateway user ID displayed on the screen.

Register and Enrol for Corporation Tax

Once your Government Gateway account is created, you must explicitly link the Corporation Tax service to it as follows:

• Log into your new HMRC Business Tax Account using your Organisation user ID.
• Navigate to the account dashboard and click “Add a tax, duty or scheme”.
• Select “Corporation Tax” from the list of options.
• Input your 10-digit UTR and your Company Registration Number (CRN).
• Enter the exact date your company started trading.
• Provide your main business address, nature of business (SIC code), and company bank details if requested.

Activate the Online Service

To prevent tax fraud, HMRC verifies your account using a physical mailing process.

• Wait for the activation code: After submitting your online registration, HMRC will post an activation code to your registered office address. This takes up to 7–10 working days to arrive.
• Complete the link: Log back into your Business Tax Account within 28 days of the letter’s date, enter the code, and fully activate your Corporation Tax dashboard.

You can add other company taxes to your corporate Government Gateway, such as VAT and PAYE, should these be required.

Contact Sameday if you require any information relating to setting up a company on 020 7613 8161.