Filing Your CT600 – An Overview

If your business is set up as a company in the United Kingdom then you will more than likely have to file a corporation tax return – known as a CT600 – to HMRC.

What is a CT600?

Very simply, a CT600 refers to a company’s corporation tax return. A company will have to include a wide range of information on its CT600, ranging from basic information about the company, such as its name and tax reference number, to details relating to what income and deductions the company received and paid during the period.

Although the vast majority of companies should submit their CT600 online to HMRC, you can get a better idea of what’s contained within a CT600 by looking at a paper version of the form here.

It’s worth noting that a company may have to submit certain supplementary pages as part of its company tax return. Examples of supplementary schedules that might need to be included are CT600A, which covers loans to participators by close companies, and CT600C, which relates to group and consortium relief, although there are others out there.

In addition, a tax computation and supporting accounts will also typically be submitted as part of a company tax return. Your accountant or tax return preparer should be able to let you know which forms you should include when filing a complete corporation tax return with HMRC.

When do I need to file a CT600?

Normally, a CT600 should be filed within 12 months of the end of the company’s accounting period.

Bear in mind that if a CT600 is filed late, then a company can be subject to late filing penalties. This makes it vitally important that companies stay on top of their tax compliance requirements and try to meet all applicable filing deadlines with HMRC.

How do I submit my CT600 to HMRC?

According to legislation in place in the U.K., companies need to submit their CT600 to HMRC online. There are very limited exceptions to this requirement. In addition, a company’s tax computations and accounts are usually submitted to HMRC in iXBRL format.

Once you’ve submitted your return to HMRC, you should receive an acknowledgement that the return has been successfully received. The return is then in the hands of HMRC, who have the power to amend or enquire into the return subject to certain time limits.

Should, at a later date, a company realise that there is an error in their corporation tax return, then it should be able to amend the submitted return, subject to certain time limits. If you need to amend a CT600, it is best to speak to your accountant or tax agent for further advice.

Getting your company tax return ready

To help you convert your company’s tax return and accounts into iXBRL format, you may choose to use the services of a managed tagging services provider, such as DataTracks. DataTracks can help you complete the tagging process, regardless of whether your source documents are in excel, pdf, or word format.

To find out more about DataTracks’ range of cost-effective iXBRL tagging solutions, speak to a member of the team on 020 3608 8035 or email