Every UK limited company must register for corporation tax UK with HMRC within 3 months of starting to trade. That rule applies whether you live in London, Casablanca, Cairo, or Istanbul. Your nationality and location do not change the obligation. Miss the deadline and HMRC charges a penalty, and those penalties are getting bigger from April 2026.
This guide walks you through exactly what to do after forming your company, what documents you need, the step-by-step HMRC registration, and the mistakes non-resident founders make most often.
What Is Corporation Tax and Who Must Register?
Corporation tax is a tax on your company’s profits. It is not personal income tax. If your UK limited company makes a profit, the company pays corporation tax on that profit before anything reaches you as the owner.
Here is who must register:
- Every UK limited company that is trading, regardless of the founder’s nationality or where they live.
- Non-resident founders who own a UK company are fully included. There is no exemption for being overseas.
- Even dormant companies may need to notify HMRC of their status.
The 2026/27 rates are straightforward: 19% on profits up to £50,000 (the small profits rate), 25% on profits over £250,000 (the main rate), and marginal relief for profits between those two figures. We break the numbers down further below.
If you have not actually formed your company yet, start there first. Our guide on how to register a company in the UK covers the Companies House side, which is a separate process from HMRC.
When Do You Need to Register for Corporation Tax?
The deadline is 3 months from the date your company starts to trade. Not three months from incorporation. The clock starts when you begin business activity.
What counts as “starting to trade”:
- Selling goods or services
- Buying stock or goods to sell
- Hiring staff or paying contractors
- Issuing your first invoice
- Earning interest or managing investments
If you form a company today and sit on it for two months before your first sale, your 3-month window runs from that first sale, not from the formation date.
Penalties are rising. HMRC penalties for late corporation tax filing are doubling from April 2026. We cover the detail in our breakdown of the corporation tax late filing penalties doubled from April 2026. The short version: late registration and late filing now cost more, so treat the deadline seriously.
One tip. Companies registered with Companies House often receive a Unique Taxpayer Reference (UTR) letter automatically by post. That UTR is not the same as being registered for corporation tax. You still have to complete the enrolment yourself.
What You Need to Register (Documents and Information)
Gather these before you start. Having them ready turns a frustrating afternoon into a 20-minute job.
- Company number from Companies House (the 8-digit number on your incorporation certificate).
- Unique Taxpayer Reference (UTR), sent by HMRC by post after incorporation.
- Date your company started trading.
- Business activity and SIC code.
- Government Gateway ID. You either log in with an existing one or create a new account.
For non-residents, you do not need a personal UK address. HMRC accepts an overseas director with a UK registered office address. Most founders use a formation agent’s address for this, and all HMRC post goes there. If you are starting from scratch, LaunchPad gives you UK formation plus a registered address in one package, which solves the correspondence problem before it starts.
How to Register for Corporation Tax Step by Step
You register online through your HMRC business tax account. Here is the full process.
Step 1: Log in or create a Government Gateway account
Go to the HMRC business tax account on GOV.UK. If you already have a Government Gateway ID, sign in. If not, create one with your email. Non-residents can create an account without a UK address.
Step 2: Add your company
Enter your company number from Companies House. HMRC links your account to the correct company record.
Step 3: Enrol for Corporation Tax
Select the option to register for corporation tax. You will need your UTR from the HMRC letter at this point.
Step 4: Enter your company details
Fill in the date your company started trading, your main business activity, the SIC code, and your accounting period dates. Get the start-of-trading date right, because it drives your deadlines.
Step 5: Wait for your activation code
HMRC posts an activation code to your registered office address. This is where non-residents trip up. The code goes by physical post, not email, so your registered address has to be real and monitored.
Step 6: Activate and confirm
Once the code arrives, log back in and enter it. Your corporation tax registration is then active. Keep a note of your registration confirmation.
Non-resident note: if your registered office is a third-party UK address, confirm with your agent that they will forward or scan HMRC post quickly. A delayed activation code can push you past your deadline. Providers like Digital Pro Suite include an enhanced address and mail handling so these letters do not vanish.
What Happens After You Register?
Registration sets the schedule for everything else. Here is what follows.
- Accounting period: HMRC assigns one, usually 12 months from the start of trading.
- Corporation tax return (CT600): due 12 months after the accounting period ends.
- Payment: due 9 months and 1 day after the accounting period ends. Note that payment is due before the return, which surprises a lot of new founders.
- Records: keep your accounting records for at least 6 years from the end of the accounting period.
Payment landing before the filing deadline is the part people miss. You calculate and pay first, then file the formal return. If you want someone to handle both, our accounting and bookkeeping service covers filing, payment reminders, and record keeping.
For a wider view of what else needs doing right after you form, see our list of steps to take after incorporating your UK company.
Corporation Tax Rates in 2026 (What You Will Actually Pay)
Three bands apply in 2026/27:
- Small profits rate: 19% on profits up to £50,000.
- Main rate: 25% on profits over £250,000.
- Marginal relief: an effective rate between the two for profits from £50,000 to £250,000.
Rough examples to show the shape of it:
| Annual profit | Rate applied | Approx tax payable |
|---|---|---|
| £20,000 | 19% small profits | £3,800 |
| £50,000 | 19% small profits | £9,500 |
| £100,000 | marginal relief | around £22,750 |
| £300,000 | 25% main rate | £75,000 |
These figures are illustrative. Always confirm the exact calculation with an accountant, since marginal relief depends on associated companies and other factors.
Non-resident note: if your company is dormant and not trading, no corporation tax is payable. You may still need to file a nil return or notify HMRC of dormancy. Silence is not the same as compliance.
Common Mistakes Non-Resident Founders Make
These four errors cause most of the penalties we see.
1. Assuming Companies House registration equals HMRC registration
It does not. Forming your company and registering for corporation tax are two separate steps with two separate authorities. Companies House handles the company itself. HMRC handles tax.
2. Missing the deadline because the HMRC letter was not forwarded
HMRC posts the UTR and the activation code to your registered address. If that address is an agent who does not forward your mail, you can blow past the 3-month window without ever seeing the letter.
3. Not knowing when trading officially started
The start date drives your deadline. Pick the wrong date and your whole schedule is off. First invoice, first purchase, or first hire usually marks it.
4. Using the wrong accounting period
An incorrect accounting period means your payment and filing dates are wrong too. Check that the period HMRC assigns matches your actual trading start.
If VAT is also on your radar because you are selling into the UK or EU, read our UK VAT registration guide. Corporation tax and VAT are separate registrations, and plenty of founders need both.
What to Do If You Miss the Deadline
Do not panic, and do not ignore it. Ignoring it makes things worse.
- Register late as soon as you realise. HMRC typically applies a fixed penalty for first-time lateness, and that can escalate with further delay.
- Appeal if you have a reasonable excuse. Delayed post to an overseas founder can sometimes support an appeal, though it is not guaranteed.
- Bring in a tax agent. A registered agent can file on your behalf and deal with HMRC directly, which is faster if you are overseas.
Keeping on top of dates is far cheaper than fixing a missed one. Our UK compliance checklist for founders lays out the deadlines that matter across the year.
Frequently Asked Questions
Does a dormant company need to register for corporation tax?
A dormant company that is not trading does not pay corporation tax, but you may still need to notify HMRC of dormancy and in some cases file a nil return. Confirm your company’s status with HMRC rather than assuming nothing is required.
Do I need to register even if my company made no profit?
Yes, if your company is trading. Registration is triggered by starting to trade, not by making a profit. You register first, then report your profit or loss in your return.
Can I register for corporation tax as a non-UK resident?
Yes. Non-resident founders register the same way through the HMRC business tax account using a Government Gateway ID. You do not need a personal UK address, but you do need a UK registered office where HMRC post is received and monitored.
What is the difference between a UTR number and corporation tax registration?
The UTR is your company’s Unique Taxpayer Reference, posted automatically by HMRC after incorporation. Corporation tax registration is the separate enrolment step you complete yourself using that UTR. Having a UTR does not mean you are registered.
When do I pay corporation tax after registering?
Payment is due 9 months and 1 day after your accounting period ends. Your corporation tax return is due 12 months after the period ends, so you pay before you file.
