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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).

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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 must be filed with HMRC:

Statutory accounts

A set of accounts will usually consist of:

  • profit and loss account (income statement)
  • balance sheet (statement of financial position)
  • notes
  • directors’ report.

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 2018 must pay any Corporation Tax due by 1 October 2019 and file the return by 31 December 2019. In practice, these things are usually filed together.

If a Company Tax Return is filed late the company will incur financial 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.

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