Skip to main content
Man using calculator

How do I complete a Company Tax Return?

All limited companies must complete a Company Tax Return. The return must be sent to Her Majesty’s Revenue and Customs (HMRC) within the correct period of time.

What is a Company Tax Return?

A Company Tax Return is called a form CT600. HMRC will issue a “notice to deliver a tax return” shortly after the end of a company’s accounting period (usually the year end date).

Tax doesn't need to be taxing

We'll email you expert tips to help you manage your business finances. You can unsubscribe at any time.

How do I complete a Company Tax Return?

  • Companies must file their Corporation Tax Return online with HMRC. The documents which must be submitted alongside the CT600, are the accounts and Corporation Tax calculations.
  • Companies must register with HMRC to file online and obtain a user ID and password. You may like to ask your accountant to deal with this on your behalf.
  • Accounts must also be filed with Companies House either online or via the post (online filing is not yet compulsory). To file online companies must obtain an authentication code from Companies House (this is completely different to the one from HMRC).
  • There is an option to file jointly via the HMRC website.

You can prepare and file your own Company Tax Return. However, unless you feel completely confident in completing the return yourself, then it may be advisable to employ the services of an accountant.  

If you require further advice or help click here to find an accountant.

What information do I need to provide?

The following information must be filed with HMRC:

  • Statutory accounts

    A set of accounts will usually consist of:

  • Corporation Tax computation (calculation)

    Profits per the accounts and taxable profits are often not the same figure, there are certain figures included in the profits for accounts purposes that are not included in the profits for Corporation Tax purposes.

    A Corporation Tax computation can be used to calculate the adjusted profits for Corporation Tax purposes. The rules are complicated, and your accountant will be able to complete this for you.
  • Company Tax return

    The main information contained within the return is:

    • details about the company
    • calculation of the corporation tax due
    • details of any capital allowances claimed
    • details of any losses claimed. 

When do I need to complete a Company Tax Return?

There are different deadlines for filing the return and the payment of tax:

  1. The Company Tax return must be submitted to HMRC within 12 months after the accounting period end to which it relates.
  2. Any Corporation Tax due must be paid electronically by nine months and a day after the accounting period end.

For example – a company with a year-end 31 December 2023 must pay any Corporation Tax due by 1 October 2024 and file the return by 31 December 2024. In practice, these things are usually filed together.

If a Company Tax Return is filed late the company will incur financial penalties. It is very important that you’re always aware of the tax year dates to avoid any penalties. 

What happens if my Company Tax Return is wrong?

Changes can usually be made within 12 months of the date a return is filed. HMRC may charge financial penalties for errors made.

HMRC may carry out a compliance check to confirm that the figures which have been filed are correct.

Corporation Tax calculator

Use our handy interactive calculator to work out how much Corporation Tax you'll pay.


Please note the results on the screen are estimates only. 

Please note the results on the screen are estimates only. 

Complete a Company Tax Return FAQs

  • What is the corporate tax rate?

    The main rate of charge to corporate tax is set at 25% for the current financial year 2024/25. Not all businesses will have to pay this rate as the small profits rate is 19%. You may be able to receive reliefs to your corporate tax by either a tax deduction or claim tax credits.

  • Which tax year are we in?

    A UK tax year runs from 6 April to the following 5 April. The HMRC requires you to file your tax return and any money you owe by the 5 April deadline. There can be a second payment deadline on 31 July for income tax if you make advance payments towards your bill.

  • How to file a corporate tax return?

    You can file your company’s corporate tax return yourself or get an accountant to prepare and file it for you. In order to file your tax return, your business needs to be registered with the HMRC. You can also file your accounts with Companies House at the same time as your tax return, although this isn’t currently a requirement.

  • When is a company tax return due?

    Every tax year, a company tax return must be filed within 12 months after the end of your company tax accounting period. The corporation tax return must be paid within 9 months after the corporation tax accounting period. You’ll have to pay penalties to the HMRC if you do not file your tax returns by the deadline but can appeal against late filing penalties if you have a reasonable excuse.

End of Article
Share this content

Brought to you by:

AAT Business Finance Basics

AAT Business Finance Basics are a series of online e-learning courses covering the core financial skills every business needs. They draw from AAT’s world-leading qualifications and will quickly build your knowledge on key topics including bookkeeping, budgeting and cash flow.

Visit partner's website

Register with Informi today:

  • Join over 30,000 like-minded business professionals.
  • Create your own personalised account with curated reading lists and checklists.
  • Access exclusive resources including business plans, templates, and tax calculators.
  • Receive the latest business advice and insights from Informi.
  • Join in the discussion through the comments section.