Setting Up a Company & Tax

Key facts

Incorporate at Companies House — HMRC is notified automatically.
You must register for Corporation Tax within 3 months of becoming active (trading, receiving income, or buying/selling assets).
HMRC will issue a Unique Taxpayer Reference (UTR) for the company.
Your first Company Tax Return (CT600) is due 12 months after the end of your first accounting period.

Incorporating Your Company

A limited company is created (“incorporated”) by registering with Companies House. You can do this online at gov.uk — most applications are approved within 24 hours. You’ll need to provide:^[1]

A company name (checked against existing registrations)
A registered office address in England & Wales, Scotland, or Northern Ireland
At least one director (who can also be a shareholder)
At least one shareholder with a minimum of one share
Articles of association (you can use the model articles provided by Companies House)
A Standard Industrial Classification (SIC) code describing the company’s activity

On incorporation, Companies House issues a Certificate of Incorporation with the company’s registered number. The company legally exists from this date, but it may not start trading until later.

Registering for Corporation Tax

When a new company is incorporated at Companies House, HMRC is notified automatically. However, you must separately register for Corporation Tax within 3 months of the company becoming “active” — that is, starting to trade, receiving any taxable income, or buying and selling assets.^[2]

Registration can be done:

Online through HMRC’s service at gov.uk (you’ll need the company’s registered number and incorporation date)
By completing form CT41G, which HMRC may send to the registered office after incorporation

After registration, HMRC will issue a company UTR (Unique Taxpayer Reference) — a 10-digit number used on all Corporation Tax correspondence and payments.^[3] You’ll also need the UTR when you come to file your first CT600.

Tip: If HMRC sends you a CT41G form, respond promptly even if the company is dormant. This tells HMRC the company is inactive and avoids unnecessary follow-up letters or penalties for missing returns.^[2]

Your First Accounting Period

Your first Corporation Tax accounting period begins when the company starts trading (or first receives chargeable income) and ends on the company’s accounting reference date (year end).^[1]

By default, Companies House sets the accounting reference date to the last day of the month in which the anniversary of incorporation falls. For example, a company incorporated on 15 July 2025 would have a default year end of 31 July 2026.

You can change this date by filing form AA01 with Companies House. Common choices are:

Year End	Why Choose It?
31 March	Aligns with the Corporation Tax financial year — simplifies rate calculations
31 December	Calendar year — common for international groups
5 April	Aligns with the personal tax year — useful for owner-managed companies

First Filing & Payment Deadlines

Once you know your first accounting period, you can work out your deadlines:^[4]

Obligation	Deadline	Example (year end 31 Mar 2026)
Pay Corporation Tax	9 months and 1 day after period end	1 January 2027
File CT600 with HMRC	12 months after period end	31 March 2027
File accounts at Companies House	9 months after period end (first accounts: 21 months from incorporation)	31 December 2026
File Confirmation Statement	Within 14 days of anniversary of incorporation	Annually

First accounts deadline: New companies get extra time for their first Companies House accounts — 21 months from the date of incorporation (or 3 months from the accounting reference date if that is later). Subsequent years revert to 9 months after the period end.^[4]

Other Tax Registrations

Depending on your company’s activities, you may also need to register for:

PAYE — required before paying any directors or employees (even if the director is the sole shareholder)
VAT — compulsory if taxable turnover exceeds £90,000, or voluntary below that threshold
Construction Industry Scheme (CIS) — required if the company works as a contractor or subcontractor in construction

Frequently Asked Questions

How do I set up a limited company for tax?

Incorporate at Companies House (HMRC is notified automatically), then register for Corporation Tax within 3 months of the company becoming active. HMRC will issue a Unique Taxpayer Reference (UTR).

When is my first Corporation Tax return due?

Your first CT600 Company Tax Return is due 12 months after the end of your first accounting period. Corporation Tax must be paid earlier — 9 months and 1 day after the period end.

What is the best year end for a new company?

31 March aligns with the Corporation Tax financial year and simplifies rate calculations. 5 April aligns with the personal tax year, which is useful for owner-managed companies. 31 December is common for international groups.

Do I need to register for PAYE as well as Corporation Tax?

Yes, if your company will pay any directors or employees. You must register for PAYE before making any payments, even if the director is the sole shareholder.

Sources

Set up a limited company — GOV.UK
Set up your company for Corporation Tax — GOV.UK
Register for Corporation Tax — GOV.UK
Running a limited company: your responsibilities — GOV.UK