How to register for Corporation Tax
The three-month window after your company starts doing business, what to register with, and the filing and payment dates that start running.
Last checked 22 August 2026
Before you start
Everything here is in the post Companies House and HMRC sent.
Your company UTR — posted to the registered office within about 14 days
of incorporation.
Your company registration number and incorporation date.
The date the company started doing business.
A Government Gateway account for the company (not your personal one).
Work out when the company started doing business
The clock starts when the company becomes active — trading, buying,
selling, advertising, renting premises, or employing someone. Simply
existing at Companies House doesn't count; a company that hasn't
started anything yet is dormant for Corporation Tax.
Register within three months of starting
Sign in with the company's Government Gateway account and register for
Corporation Tax, quoting the company UTR, the start date, and the date
the annual accounts are made up to.
Register on GOV.UK →Deadline
Within 3 months of the company starting business activity — later
than that risks a failure-to-notify penalty.
Understand the accounting period it creates
Registration opens your first Corporation Tax accounting period,
normally running from the start date to your accounting reference
date. A first period longer than twelve months gets split into two
returns — twelve months plus the remainder — which is normal for new
companies.
Diary the payment date — it comes before the return
Corporation Tax is due 9 months and 1 day after the end of the
accounting period, but the return itself isn't due until 12 months
after. For financial year 2026 the small profits rate is 19% up to
£50,000 of profit and the main rate 25% above £250,000, with marginal
relief in between.
Deadline
9 months and 1 day after the accounting period ends — the payment
deadline, three months before the return is due.
File the CT600 return with accounts
The company tax return goes to HMRC with full statutory accounts and
tax computations, filed online. Statutory accounts also go to
Companies House on their own deadline — nine months after the
accounting year end for a private company.
Register the other schemes the company needs
Paying yourself a salary means a PAYE scheme; passing the VAT threshold
means VAT registration. Neither happens as part of Corporation Tax
registration.
Common questions
Company tax, in practice
My company isn't trading yet — do I still register?
Tell HMRC the company is dormant instead. When it becomes active,
register within three months of that date; the dormant years need no
Corporation Tax returns once HMRC has agreed the status.
Is the company UTR the same as my personal one?
No — the company has its own 10-digit UTR for Corporation Tax,
separate from any personal UTR you hold for Self Assessment. Directors
don't automatically need Self Assessment, but dividends or other
untaxed income can bring you into it personally.
I never received the company UTR — where is it?
It went to the registered office shortly after incorporation. You can
request a copy online from HMRC and it's re-posted to the registered
office, so check that address is right first.
When do I pay — before or after filing?
Usually you prepare the accounts well before either deadline, then pay
by 9 months and 1 day and file by 12. Paying on an estimate and
correcting when the return goes in beats missing the payment date,
because interest runs from it.
Related guides
What new companies set up next.
How to register as an employer for PAYE
When you need a PAYE scheme, how to register with HMRC in time for your first payday, and the references that arrive when you do.Read the guide →
How to register for VAT
When registration becomes compulsory, how to apply online, and what changes from your effective date — including charging VAT before your number arrives.Read the guide →
Company registered? Keep the books statutory-ready.
Bookfolio keeps a limited company's records on the accrual basis HMRC expects, tracks Corporation Tax as profits build, and prepares the figures your accounts and CT600 are made of.