Step-by-Step Guide to Register Your Company for UK Corporation Tax with HMRC

In this guide, we will walk you through who needs to register, when your clock starts ticking, and how to complete the registration process online. Whether you are a first-time founder or managing multiple businesses, we will ensure you are on the right track to stay compliant with HMRC and avoid costly mistakes.

Do Your Company Needs to Register for Corporation Tax

You must register if your company is:

• A UK limited company or Non-Resident Companies that has started trading or earning income
• An overseas company with a UK branch or office making taxable profits
• An active unincorporated association, club, or co-operative

Earning income means making money through business activities. For example, when a company sells goods or services, rents out property, or receives any form of payment for its business operations, that’s considered earning income.

HMRC considers your company active when it starts trading, such as buying/selling goods or renting property. Dormant companies don’t need to register until trading begins. For property companies, this could be when you purchase property or start receiving rent.

What You Need Before Registering for Corporation Tax

You must inform HMRC within three months of your company starting to trade. The Corporation Tax deadline is based on your trading start date, not your incorporation date. After incorporation, HMRC will send a Unique Taxpayer Reference (UTR) letter to your registered office. However, receiving this letter does not mean you're registered, you still need to complete your Corporation Tax registration online.

Before you begin, ensure you have the following:

• Your UTR number
• Your Companies House registration number
• The date your company started trading
• The date your first accounts are due (Usually 21 months after the incorporation date)
• Access to your company's Government Gateway account

By registering on time, you ensure your company stays on track with its tax responsibilities, avoiding costly penalties for late registration.

How to Register for Corporation Tax with HMRC

Registering your company for Corporation Tax online is the fastest way to manage your tax and avoid penalties. If you're a UK limited company or non-resident company, you must notify HMRC within three months of starting to trade, even if you haven’t made a profit yet.

When registering with Companies House, you have the option to set up Corporation Tax at the same time. If not, you’ll need to add Corporation Tax services to your business tax account.

A UK limited company or non-resident company must notify HMRC within three months of starting to trade, even if no profit has yet been made.

Registering Multiple SPVs: What Portfolio Landlords Need to Know

If you hold a property portfolio through several special purpose vehicles (SPVs), each company must be registered separately for Corporation Tax with HMRC. HMRC treats every limited company as its own legal taxpayer, so each SPV will have its own Unique Taxpayer Reference (UTR), its own Corporation Tax record and its own set of filing and payment deadlines.

Each company must have its own gateway account, and you must add each company individually using its own UTR when you enrol for Corporation Tax online. Keep clear records of each company’s trading start date, registration deadline, accounting period end date, filing deadline and payment date. Missing a deadline for one SPV will not be covered by registration for another, and HMRC applies deadlines and penalties on a company by company basis.

Because each SPV will usually incorporate and start trading at different times, the three month window for registering with HMRC runs independently for every company. Do not assume that registering one SPV automatically registers the others. 

Post-Registration Obligations for Corporation Tax: Filing, Payment and Records

Once your company is registered for Corporation Tax, you must file the CT600 tax return within 12 months of your accounting period end, even if there’s no profit. Corporation Tax is due nine months and one day after the accounting period ends, with interest charged for late payments. The rate is 19% for profits up to £50,000, 25% for profits above £250,000, and a tapered rate applies for profits between £50,000 and £250,000. If your company is part of a group of associated companies, the upper limit (£250,000) and lower limit (£50,000) for these rates are divided by the total number of companies in the group, which impacts the thresholds and rates applied.

For companies with profits over £1.5 million, quarterly payments are required, but the filing deadline remains the same for all companies at 12 months after the accounting period ends. Stay on top of these deadlines to avoid penalties.

When Registration Is Not Required for Dormant Companies

A dormant company that hasn’t started trading doesn’t need to register for Corporation Tax until it becomes active. However, it’s important to note that HMRC’s definition of dormancy i.e.  A company is considered dormant for Corporation Tax if it has stopped trading and has no other income (e.g., from investments), is a new limited company that hasn’t started trading, an unincorporated association or club owing less than £100 in tax, or a flat management company not involved in trading.

Once a dormant company begins trading, you must register with HMRC within three months. If the company stops trading and becomes dormant again, you must inform HMRC to avoid unnecessary filing reminders. Unless you receive a notice from HMRC stating that you do not need to file a return, the company must continue to file the Corporation Tax return even if it is dormant. When the company resumes trading, update your registration details with HMRC so they can reset your deadlines accordingly. Keeping HMRC updated ensures your company stays compliant and avoids penalties.

Notification of Liability form HMRC

Failing to notify HMRC that your company is liable for Corporation Tax can result in penalties, even if no tax is owed. Known as a 'failure to notify' penalty, it depends on the amount of tax owed and whether the failure was deliberate.

Penalties are calculated based on the potential lost revenue (PLR). If the failure was careless, the penalty can be up to 30% of the PLR. For deliberate actions, it rises to 70%, and for deliberate and concealed failures, it can reach 100%. However, penalties may be reduced if you notify HMRC promptly and disclose all relevant information. Additionally, if the company has reasonable grounds for failing to notify on time, and corrects the error quickly, the penalty may be reduced or waived.

Walkthrough Example: Property SPV from Incorporation to First Filing

This example shows how key Corporation Tax dates work for a property Special Purpose Vehicle (SPV) under HMRC rules.

Common Mistakes to Avoid When Resgistering for Corporation Tax

• Assuming Companies House incorporation counts as Corporation Tax registration. It does not. They are separate processes.
• Calculating the three-month deadline from your incorporation date rather than your trading start date.
• Misjudging when your company became active. Activities such as advertising, placing orders for stock, or hiring staff may mean trading has already started.
• Submitting incorrect information, such as the wrong trading start date or SIC code, which can cause misaligned deadlines and require correction with HMRC.
• Using your personal Government Gateway ID instead of a company account when enrolling.

Conclusion

Registering for Corporation Tax is a legal obligation for all UK limited companies once they become active. The three-month deadline begins from the start of your trading activity, not the incorporation date, and must be completed online through HMRC’s Government Gateway using your company’s UTR and trading start date.

After registration, your company must file its CT600 tax return within 12 months of the end of the accounting period and pay any Corporation Tax owed within nine months and one day. If you manage multiple SPVs, each company must register separately using its own UTR, though you can manage them all through a single Government Gateway account.

HMRC, the government agency responsible for the UK's tax system, oversees all Corporation Tax registrations, filings, and payments. By staying on top of these obligations, you ensure your company remains compliant, avoids penalties, and keeps its operations running smoothly.

Frequently Asked Questions