Accountant For A Limited Company

How to Register for Corporation Tax?

A new UK limited company is automatically registered for Corporation Tax when incorporated through Companies House, and HMRC posts a 10-digit UTR to the registered office within 14 days. Directors must then notify HMRC the company is active within 3 months of starting to trade, using the Government Gateway. Dormant companies tell HMRC separately and do not file a CT600 until trading begins.

How to Register for Corporation Tax? - Step-by-step Guide - GoForma Tax Guides | UK Accountants & Tax Advisors
This article is part of our Accountant For A Limited Company guide — your essential resource for running a limited company.

Key takeaways

  • Companies incorporated through Companies House are automatically registered for Corporation Tax, and HMRC posts a 10-digit UTR to the registered office within 14 days of incorporation.
  • Directors must tell HMRC the company is active within 3 months of starting to trade, advertising, employing staff, renting premises or earning any taxable income.
  • Activation is completed online through the Government Gateway business tax account using the UTR, company registration number and the date trading began.
  • Dormant companies notify HMRC in writing that they are not trading and do not need to file a CT600 Company Tax Return until trading actually starts.
  • Late notification triggers failure-to-notify penalties under Schedule 41 Finance Act 2008, which can reach 100% of the Corporation Tax due where behaviour is deliberate and concealed.

Registering for Corporation Tax

Starting a new business can be stressful, there are so many things to consider. One of the most important things to take care of is registering for corporation tax. It's essential that you get this right from the start. In this blog post, we will cover what corporation tax is and why it's essential to register for it. We'll then guide you through the step-by-step process of registration, from pre-registration requirements to post-registration steps.

Why Register a Company for Corporation Tax?

You require to register a new company for the corporation tax within the 3 months of starting your business which includes:

  • carrying on a business activity such as a trade or professional activity
  • buying and selling goods with a purpose to making a profit
  • providing professional services
  • earning interest
  • managing investments
  • receiving any other income

Note that writing a business plan to get your business set up do not count as the start of your trading period.

What is Corporation Tax?

Corporation tax, a direct tax levied on a company's profits, includes taxable profits, chargeable gains, and the company's income. To comply with tax laws, companies must register for corporation tax, allowing them to report taxable profits, calculate tax liability, and pay tax to HMRC. It is the legal requirement of the company to work out how much corporation tax is payable.

Why is Registering for Corporation Tax Essential?

Registering for corporation tax is crucial for companies to comply with legal tax requirements and avoid penalties. It enables companies to file tax returns and pay their tax liability to HMRC, contributing to government revenue. Understanding the amount of corporation tax owed is vital for effective tax planning and financial management.

When to Register for Corporation Tax?

Most companies registers for the corporation tax and PAYE as an employer at the same time while registering the company for Companies House. But, if you have registered your company by post, through an agent, or using third-party software, you'll need to register for Corporation Tax separately. Make sure you register within 3 months of starting your business.

What Information will I Need to Register for Corporation Tax Online?

  • Your company registration number - You can get it from the certificate of incorporation.
  • Business start date - The date when the business became active. Your company’s first accounting period will start from this date
  • Year end date - Date to which annual accounts will be prepared
  • Your company's unique taxpayer reference (UTR) number.
  • Company name and company address
  • Nature of the business
  • Name and address of the company directors

How to Register for Corporation Tax?

  1. Sign in to your business tax account using your Government Gateway user ID and password to register for Corporation Tax. If you do not have a government gateway account user ID, you can create one when you sign in.
  2. HMRC will verify your Corporation Tax registration within seven days. You will receive an Activation Code (or PIN) at your registered office address. Activate your HMRC online services as soon as you get this code as the code remains valid only for a short period of time.
  3. The information you provide to HMRC will be used to determine your company’s corporation tax accounting period and your deadlines for filing Company Tax Returns and paying Corporation Tax.
  4. Also register for Value Added Tax (VAT) and set up your online VAT account with HMRC if the company's VAT-taxable turnover is more than £90,000 (VAT registration threshold for 2024/25 tax year) in a 12-month accounting period.
  5. Register PAYE for Employers at the same time as registering for Corporation Tax online.

What Happens After Registering for Corporation Tax:

After successful registration, HMRC will issue a Corporation Tax reference number. You'll then be required to:

  1. Maintain Records: Keep accurate financial records in accordance with HMRC guidelines.
  2. Submit Annual Tax Returns: File your Corporation Tax return annually, providing details of your company's profits and any applicable deductions. You need to file a Company Tax Return, even if you make a loss or have no Corporation Tax to pay. This should be done within 12 months after your accounting period ends.
  3. Pay Corporation Tax: You are responsible to calculate your corporation tax you owe and pay it. Use our Corporation Tax Calculator to work out how much tax you need to pay. You must pay within 9 months and 1 day from the end of your 'accounting period' - which is usually your financial year.

What Accounting Records Do I Need to Keep?

  1. Annual accounts, including profit and loss (income statement)
  2. Bank statements, paying in slips, cheque books and details of amounts paid or received electronically
  3. Cash books and other account books
  4. Purchase and sales invoices
  5. Credit or debit notes (issued or received)
  6. Order and delivery notes
  7. Records of daily earnings
  8. Payroll records
  9. VAT records

Corporation Tax Payment Deadline

A company must pay the corporation tax online by nine months and a day after the accounting period end. For example, if a company's year-end is 31 December 2025, it must pay any corporation tax due by 1 October 2026.

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Frequently asked questions

When must a new company register for Corporation Tax?

A UK limited company must tell HMRC it is active within 3 months of starting any business activity. HMRC counts the company as active from the date it starts trading, advertising, buying or selling goods, employing staff, renting premises or earning investment income. Writing a business plan or opening a bank account does not count. The 3-month deadline runs from the first of these activities, not the incorporation date at Companies House.

Do I have to register separately if I formed the company through Companies House?

Usually not. When you incorporate a limited company online through Companies House, the details are passed to HMRC automatically and the company is registered for Corporation Tax at the same time. HMRC then posts a 10-digit UTR to the registered office within 14 days. If you incorporated by post, through a third-party formation agent or using software that did not share data with HMRC, you must register for Corporation Tax separately once trading starts.

What is a Corporation Tax UTR and how do I get one?

A UTR, or Unique Taxpayer Reference, is the 10-digit number HMRC uses to identify your company for Corporation Tax. It is posted to the registered office address shown on the Companies House record within 14 days of incorporation, inside a letter titled 'Information for new companies'. If the UTR never arrives or is lost, you can request a copy through the 'Find your UTR' service on GOV.UK or by signing in to the business tax account.

What counts as the company becoming 'active' for Corporation Tax?

HMRC treats a company as active once it starts any activity aimed at making a profit or earning income. This includes trading, advertising for customers, buying stock, hiring employees, renting premises, providing services, receiving interest or investment income, and managing investments. Preliminary steps such as registering the company, writing a business plan or setting up a bank account do not count. The first active date sets the start of the first Corporation Tax accounting period.

How do I register for Corporation Tax online with HMRC?

Sign in to the business tax account at GOV.UK using your Government Gateway user ID, or create one if you do not have it. Add Corporation Tax as a service using the company's 10-digit UTR, company registration number and the date it started trading. HMRC then confirms the accounting period and issues online filing access. You must submit this notification within 3 months of the company becoming active, even if you use an accountant to file the return later.

What happens if my company is dormant and not trading yet?

A dormant company has no taxable income, expenses or Corporation Tax liability. You tell HMRC the company is dormant by signing in to the business tax account or writing to the Corporation Tax office using the UTR. Dormant companies do not need to file a CT600 Company Tax Return until they start trading. Companies House still requires annual confirmation statements and dormant company accounts, which are separate filings from Corporation Tax.

What happens after I register, and when is Corporation Tax due?

Once registered, HMRC confirms your accounting period, usually your company's financial year. You must file a CT600 Company Tax Return within 12 months of the accounting period end and pay any Corporation Tax due 9 months and 1 day after the period end. For a year ending 31 December 2025, tax is payable by 1 October 2026 and the return is due by 31 December 2026. Payment and filing have separate deadlines.

What are the penalties for registering late or missing the 3-month deadline?

HMRC can charge a failure-to-notify penalty under Schedule 41 Finance Act 2008 where a company does not register for Corporation Tax on time. The penalty is a percentage of the Corporation Tax unpaid on the due date: up to 30% for careless errors, 70% for deliberate failures and 100% where the failure is deliberate and concealed. Telling HMRC before they ask, and paying on time, can reduce the penalty significantly.

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