Step-by-Step: Register for Corporation Tax

New UK companies must register for Corporation Tax when they become active. HMRC treats a company as active when it starts doing business activities such as buying or selling goods or services, advertising, employing staff, renting property, earning bank interest or managing investments. Registration is not the same as incorporation. Companies House creates the company, but you still need to tell HMRC when trading begins so your Corporation Tax record and deadlines are set correctly. Shortly after incorporation HMRC issues a Company Unique Taxpayer Reference (UTR) by post to the registered office; you will need this to register.

Failure to register on time risks late filing penalties, interest on late paid tax and avoidable HMRC correspondence. Getting the set-up right at the start also prevents knock-on errors with your first accounting period, CT600 return and payment timetable.

What this article is about: this is a practical, step-by-step guide that explains when you must register, the information HMRC will ask for, how to complete the online process, and what happens next. We cover how “active” status works in practice (noting that some pre-trading spend alone may not trigger registration), how to align your Corporation Tax accounting period with your financial year, what to do if the company is dormant, and the common mistakes that lead to penalties. The guide is written for owners, finance directors and senior managers who want clean, compliant set-up with no surprises.

By the end, you will know exactly when to register, what documents to have to hand, how to navigate the Government Gateway and HMRC online service, and how to avoid the traps that cost time and money later.

 

 

Section A: Understanding Corporation Tax Registration

 

Corporation Tax registration is a legal requirement for companies operating in the UK. Once a business becomes active, HMRC expects it to register so that taxable profits can be assessed and statutory filing deadlines issued. This process is separate from incorporating the company at Companies House. Incorporation creates the legal entity; registration establishes the company’s Corporation Tax record and obligations.

The obligation to register arises under UK tax legislation and HMRC practice, which enforce compliance through statutory deadlines and penalties for late or inaccurate notification. For owners and directors, the priorities are understanding which organisations must register, what “active” means for Corporation Tax, and why timing matters.

Entities that may be required to register include:

• UK-incorporated limited companies
• Overseas companies with a UK permanent establishment
• Members’ clubs, societies, and associations that generate taxable profits
• Trade associations and housing associations operating as corporate entities

 

“Active” has a specific meaning for HMRC. A company is generally active when it begins business activities with a view to making profit or receives income—for example buying or selling goods or services, employing staff, advertising to customers, managing investments, or renting property. Some pre-trading expenditure alone may not always trigger registration, but issuing invoices, hiring staff, commencing sales or marketing, or beginning chargeable activities typically will. By contrast, a dormant company that has not yet commenced activity does not need to register until trading begins.

Timely registration matters because HMRC uses the activity start date to set the company’s Corporation Tax accounting period. This determines deadlines for the first company tax return (CT600) and for payment. Late or missed registration can result in estimated tax assessments, penalties, and interest, even where profits are modest.

Section Summary: Registration is mandatory once a company is active in the UK. Understanding HMRC’s definition of “active” is critical, as it triggers the duty to register and sets the accounting period and deadlines. Acting promptly avoids penalties and administrative complications.

 

 

Section B: When and How to Register

 

The rules on Corporation Tax registration are strict. Every company that becomes active in the UK must notify HMRC within three months of starting to trade. Missing this deadline exposes the business to automatic penalties, regardless of whether the company is profitable. Knowing when to register and how to complete the process ensures compliance from the outset.

 

1. Registration Deadlines

 

HMRC requires companies to register within three months of becoming active. The test for “active” is not incorporation but the start of activities with a view to generating income. Examples include:

• Selling goods or services
• Advertising the business to potential customers
• Employing staff or engaging contractors
• Managing investments or property
• Receiving bank interest or other income

 

Dormant companies, which have no trading activity, do not need to register until they become active. HMRC should be informed if a company is dormant to avoid unnecessary notices to file returns.

 

2. Step-by-Step Registration Process

 

The process of registering for Corporation Tax is handled online through HMRC’s service. The steps are:

1. Create Government Gateway credentials – Directors or authorised agents must have a Government Gateway user ID and password to access HMRC services.
2. Obtain the Company UTR – HMRC issues a Unique Taxpayer Reference automatically soon after incorporation, posted to the registered office address.
3. Log into HMRC’s Corporation Tax registration service – Use the Government Gateway to access the online portal.
4. Provide company information – This includes company name and registration number, UTR, date business activities began, main business activity (SIC code), and the accounting reference date.
5. Confirm authorised contacts – Supply details of the director or adviser responsible for tax affairs.
6. Submit the registration – Once submitted, HMRC sets up the Corporation Tax record and online account.

 

 

3. What Happens After Registration

 

When registration is accepted, HMRC will:

• Confirm the company’s Corporation Tax accounting period
• Provide access to the Corporation Tax online account through Government Gateway
• Issue notices to file company tax returns (CT600) for each accounting period
• Set deadlines for payment of Corporation Tax, usually nine months and one day after the period end

 

The online account is also used to file returns, pay Corporation Tax, and update details such as changes to accounting periods or dormant status.

Section Summary: Companies must register with HMRC within three months of becoming active. Registration is completed online using Government Gateway credentials and the company UTR. Once registered, HMRC sets the accounting period, issues filing notices, and opens access to the online account.

 

 

Section C: Common Issues and Mistakes

 

Even when directors understand the obligation to register for Corporation Tax, mistakes are common. HMRC applies penalties strictly, meaning that oversights can cost money and damage compliance records. Anticipating the issues that most often trip up businesses will help avoid unnecessary fines and administrative problems.

 

1. Missing the Deadline

 

The most frequent mistake is failing to register within three months of the company becoming active. Many owners wrongly assume that incorporation at Companies House automatically covers tax registration, but this is not the case. Missing the deadline can result in penalties even if the company is not yet profitable. HMRC can also issue estimated tax bills based on assumed profits, creating administrative headaches for the business.

 

2. Not Understanding ‘Active’ Status

 

A second common error is misjudging when a company is deemed active. Businesses sometimes delay registration because they believe trading has not yet started, but HMRC’s definition of activity is broader. Activities that may trigger registration include:

• Issuing invoices or receiving income
• Buying stock or raw materials
• Advertising services or products
• Hiring staff or contractors
• Managing or renting out property

 

Even without revenue, these activities may mean the company is active for tax purposes. By contrast, a dormant company with no activity does not need to register until trading begins. Some pre-trading expenditure alone may not automatically trigger registration, but once commercial activity commences, registration is mandatory.

 

3. Incorrect Information Submitted

 

Errors in the registration form can cause compliance issues later. Submitting the wrong Standard Industrial Classification (SIC) code may prompt HMRC queries or misaligned record-keeping. Likewise, using an incorrect start date or accounting reference date can distort deadlines for Corporation Tax filing and payment. Mistakes require correction through HMRC, which can be time-consuming and potentially lead to penalties if not promptly resolved.

Section Summary: The three main traps for businesses are missing the registration deadline, misunderstanding HMRC’s definition of “active,” and submitting inaccurate information. Taking care at the outset avoids penalties and keeps records aligned with HMRC requirements.

 

 

Section D: Compliance and Ongoing Duties

 

Registering for Corporation Tax is only the first step. Once HMRC recognises a company as active, it must meet ongoing compliance duties. These include filing tax returns, paying Corporation Tax, and keeping HMRC informed about any changes in the company’s trading status. Directors remain legally responsible for meeting these duties, even where professional advisers manage the administration.

 

1. Filing Corporation Tax Returns

 

Every active company must file an annual company tax return (CT600) with HMRC. The return details taxable profits, adjustments, and any reliefs or allowances claimed, supported by statutory accounts and a tax computation. The deadline for filing is 12 months after the end of the accounting period. HMRC issues a notice to deliver a return, but the obligation exists even if no notice is received. Late filing attracts automatic penalties which escalate if delays persist.

 

2. Paying Corporation Tax

 

Corporation Tax is usually due nine months and one day after the end of the accounting period. This payment deadline is earlier than the filing deadline, so companies must prepare tax figures promptly. HMRC accepts Faster Payments, CHAPS, Bacs, and direct debit. Interest accrues on late payments and persistent non-compliance can trigger additional penalties. Large companies may be required to pay in quarterly instalments, with the first due six months and 13 days after the start of the accounting period.

 

3. Changing Company Status

 

Companies must notify HMRC if their trading status changes. Where a company becomes dormant, HMRC should be informed to avoid unnecessary filing obligations. Similarly, when a dormant company resumes trading, registration details must be updated so that HMRC can reset deadlines. Failure to update HMRC can lead to incorrect notices and penalties.

Section Summary: Ongoing compliance means filing annual returns on time, paying Corporation Tax within strict deadlines, and updating HMRC on trading status. Consistent compliance avoids penalties, interest, and administrative disputes with HMRC.

 

 

FAQs

 

When should I register for Corporation Tax?
You must register within three months of your company becoming active. Activity includes trading, advertising, employing staff, or managing investments. Incorporation alone does not count as registration.

How do I know if my company is active for tax purposes?
HMRC considers a company active if it starts business activities with a view to making profit, even if revenue has not yet been received. Examples include issuing invoices, buying stock, or hiring staff. Some pre-trading expenditure alone may not trigger registration, but once trading or commercial activity begins, you must register.

Can I register a dormant company?
No. A dormant company does not need to register until it becomes active. If its status changes, you must inform HMRC immediately so deadlines can be set correctly.

What happens if I miss the three-month deadline?
HMRC can impose penalties for late registration and may issue estimated tax bills. Interest will also be charged on late payments of Corporation Tax.

Do overseas companies need to register?
Yes. Overseas companies with a UK permanent establishment — such as a branch or office generating taxable profits — must register with HMRC for Corporation Tax.

 

 

Conclusion

 

Registering for Corporation Tax is a fundamental legal obligation for UK companies once they become active. The process is separate from incorporation and must be completed within three months of starting to trade to avoid penalties. HMRC uses the registration details to set the company’s accounting period, filing requirements, and payment deadlines.

Timely and accurate registration creates a strong foundation for compliance. From that point, companies must meet ongoing duties: filing the annual CT600, paying Corporation Tax on time, and informing HMRC of any change in status. Larger companies should also be mindful of quarterly instalment payment obligations.

Key takeaway for directors and finance leaders: understand when your company becomes active, gather the right details for registration, and keep ahead of deadlines. Doing so prevents unnecessary costs and helps maintain a clean compliance record with HMRC.

 

 

Glossary

 

Term	Definition
Corporation Tax	A tax on the taxable profits of UK limited companies and certain other corporate entities.
Company UTR	The Unique Taxpayer Reference issued by HMRC to identify a company for tax purposes, posted to the registered office shortly after incorporation.
HMRC	His Majesty’s Revenue and Customs, the UK government body responsible for tax collection and enforcement.
Government Gateway	The UK government’s secure online system for accessing HMRC and other public services.
SIC Code	Standard Industrial Classification code describing a company’s main business activity.
CT600	The company tax return form submitted annually to HMRC detailing Corporation Tax liability, supported by accounts and a tax computation.

 

 

Useful Links

 

Resource	Link
GOV.UK – Register for Corporation Tax	Register for Corporation Tax
GOV.UK – Corporation Tax	Corporation Tax overview
GOV.UK – File your company tax return	File a Company Tax Return (CT600)
Taxoo – CT600 Guide	CT600 Guide
Taxoo – Corporation Tax Payment Deadlines	Corporation Tax Payment Deadlines