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.

Corporation Tax registration deadline

Time limit for registering a new company for Corporation Tax with HMRC.

Registration deadline: Within 3 months of starting to do business
What counts as starting: Buying, selling, advertising, renting property, employing someone
UTR delivery: 10-digit Unique Taxpayer Reference sent by post after incorporation

Set up your company for Corporation Tax

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.
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.
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.
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.

Register for Corporation Tax

How to register your limited company for Corporation Tax with HMRC.

Registering a company with Companies House does not automatically register it for Corporation Tax. Separate registration with HMRC is required within 3 months of starting to trade.

When to register

'Starting to trade' means when a company:

Buys, sells, or advertises goods or services
Employs someone
Hires or rents property or equipment
Starts charging for goods or services

Not considered trading: Registering the company name, setting up a bank account, or conducting market research.

Registration deadline: Within 3 months of starting to trade
Penalty for late registration: Penalties apply for late registration - contact HMRC for specific amounts
Corporation Tax UTR: 10-digit Unique Taxpayer Reference sent within 15 working days
Activation code: Posted within 10 working days (21 if abroad)

Registration process

Wait for Companies House confirmation - Company registration number is required
Register for Corporation Tax online - Most new companies are automatically registered when incorporated. If not, use the online service to add Corporation Tax to your business tax account
Provide company details - Company number, business start date, first accounting period end date
Receive Corporation Tax UTR by post within 15 working days
Receive activation code by post within 10 working days (21 if abroad)
Activate online account using UTR and code

What happens after registration

File annual Company Tax Return (CT600): Due within 12 months of year-end
Pay Corporation Tax: Due 9 months and 1 day after year-end
Keep accounting records: For at least 6 years
Annual confirmation: HMRC sends annual reminder when your return is due

Corporation Tax rates 2025/26: 19% on profits up to £50,000 | 25% on profits over £250,000 | Marginal relief between £50,000-£250,000
First accounting period: Can be up to 18 months (typically 12 months)
Payment deadline: 9 months and 1 day after accounting period ends

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.

Corporation Tax rates and allowances 2025/26

Current Corporation Tax rates and thresholds for limited companies, including main rate, small profits rate, and marginal relief band.

Main rate (25%): Applies to profits over £250,000 (from 1 April 2023)
Small profits rate (19%): Applies to profits of £50,000 or less
Lower threshold: £50,000 (small profits rate eligibility)
Upper threshold: £250,000 (main rate applies above this)
Marginal relief band: £50,000 to £250,000 (tapered effective rate 19%-25%)
Associated companies rule: Thresholds divided equally by number of associated companies

The Corporation Tax rate structure changed significantly from 1 April 2023 under Finance Act 2022. The main rate increased from 19% to 25% for profits over £250,000, while small companies with profits up to £50,000 retained the 19% rate. Companies with profits between £50,000 and £250,000 benefit from marginal relief, which provides a gradual transition between the two rates.

Associated companies: If you have associated companies (connected businesses under common control), the profit thresholds are divided equally by the total number of companies. For example, with 2 associated companies, the small profits threshold becomes £25,000 each.

Corporation Tax rates

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.

Business Context Testing

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Register your company for Corporation Tax

Who must register

Gather your information

Register online with HMRC

Confirm your accounting period

Set up your HMRC online account

What happens after registration

Late registration

Compliance Assistant

🧪 Business Context Testing

◉ Content Graph

Who must register

Gather your information

Register online with HMRC

Confirm your accounting period

Set up your HMRC online account

What happens after registration

Late registration

Related guides in Tax & Finance

Business Context Testing

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