Register for Self Assessment
When and how to register for Self Assessment tax.
Corporation Tax
UK-wide
Register your company for Corporation Tax
Step-by-step Corporation Tax registration for new companies.
Guide summary
You must register your company for Corporation Tax within 3 months of starting any business activity, such as buying, selling, advertising, renting property, or employing someone. Use your Government Gateway account to register online. You'll need your Unique Taxpayer Reference (UTR) and company details. After registration, you must file a Company Tax Return (CT600) each year and pay any tax due 9 months and 1 day after your accounting period ends.
- Register for Corporation Tax within 3 months of starting business activity
- Get your 10-digit UTR from HMRC by post within 15 working days
- Use Government Gateway to register online
- Choose your accounting period end date (usually 31 March or incorporation anniversary)
- Activate your online account with the activation code sent by post
- File Company Tax Return (CT600) within 12 months of year-end
- Pay Corporation Tax 9 months and 1 day after year-end
- Keep accounting records for at least 6 years
- Small profits rate 19% (profits £50,000 or less); main rate 25% (profits over £250,000)
- Marginal relief applies for profits between £50,000 and £250,000
On this page
Related guides in Tax & Finance
How taxes work for limited companies
Understanding Corporation Tax, VAT, PAYE, and Self Assessment - how they interconnect and your obligations to Companies House …
Change from sole trader to limited company
How to incorporate your sole trader business as a limited company. Covers the incorporation process, transferring assets, tax …
Corporation tax rates and small profits relief
Understanding the Corporation Tax rate structure following Finance Act 2021 changes. Covers the 25% main rate, 19% small …
Associated companies and Corporation Tax
How associated companies rules affect your Corporation Tax rate thresholds and quarterly instalment obligations.
Who must register
All UK limited companies must register for Corporation Tax with HMRC. You must do this within 3 months of starting any business activity, including buying, selling, advertising, renting a property, or employing someone.
A newly incorporated company that has not yet started trading does not need to register immediately, but must register as soon as it begins any taxable activity.
-
1
Gather your information
You will need: your company's Unique Taxpayer Reference (UTR) from HMRC, date of incorporation, date you started or intend to start business activity, your company's registered office address, the nature of your business, and your accounting period end date.
-
2
Register online with HMRC
Use your Government Gateway account to register for Corporation Tax. If your company was incorporated at Companies House, HMRC will have already sent a UTR by post within about 2 weeks of incorporation.
-
3
Confirm your accounting period
Choose your accounting period end date. Most companies use 31 March (aligning with the tax year) or their incorporation anniversary. This determines your CT600 filing and payment deadlines.
-
4
Set up your HMRC online account
Once registered, activate your Corporation Tax online service to file returns and view your account. You will need the activation code HMRC sends by post, which takes 7-10 working days.
What happens after registration
After registration, HMRC will confirm your Corporation Tax reference and accounting period. You will receive a notice to deliver a Company Tax Return (CT600) shortly after your first accounting period ends.
Late registration
There is no specific penalty for late Corporation Tax registration. However, if you file your CT600 late or pay Corporation Tax late because you were not registered, the normal late filing penalties and late payment interest apply. Registering promptly avoids these risks.