Reviewed by Connor Masters ATT, Senior Tax Specialist at RIFT Tax Refunds

A CT600 form is an important document for UK businesses. It’s used to calculate how much Corporation Tax you owe HMRC as part of the Company Tax Return process. It helps to ensure that you pay the correct amount of tax based on your profits.

What is a CT600 form?

A CT600 form is used to report your company’s profits or losses in a financial year. It’s one part of the Company Tax Return that you must return to HMRC when you receive a notice to deliver one.

Along with any supporting information such as supplementary pages, accounts and computations, the form helps HMRC determine how much Corporation Tax your company owes.

Who needs to submit a CT600 form?

Every business that’s registered in the UK with Companies House must submit a CT600 form every year as part of a Company Tax Return.

Organisations that must complete the return include:

  • Limited companies registered in the UK
  • Foreign companies with a UK branch or office
  • Unincorporated members’ clubs, societies and associations
  • Trade associations
  • Housing associations
  • Charities and non-profit organisations
  • Community amateur sports clubs

It’s a legal requirement to submit a CT600 form, irrespective of whether there’s any tax to pay.

When is the CT600 form due?

The deadline for submitting a CT600 form is usually 12 months after the end of your company's accounting period. For example, if your accounting period ends on 31 March, the form will be due by the same day the following year.

Corporation Tax meanwhile is due nine months and one day after the end of your accounting period.

What happens if I submit my CT600 late?

You will have to pay a penalty if you fail to submit your CT600 on time, which increases the longer you leave it.

Late By Penalty
1 day £100
3 months Another £100
6 months HMRC will estimate your Corporation Tax bill and add a penalty of 10% of the unpaid tax
12 months Another 10% of any unpaid tax

How to complete the CT600 form

It may look a little complicated at first glance, but completing the CT600 form is all about having the right information to hand. 

Step 1: Preparation

To complete the CT600 form, you'll need: 

  • Your profit and loss accounts 
  • Your balance sheet 
  • Details of any adjustments to profits 
  • Information on any capital allowances 
  • Details of any reliefs and deductions 

Step 2: Access and download the CT600 form

You can access and download the CT600 form from the HMRC website. 

Step 3: Complete the CT600 form

Fill out the form with your company’s financial details. Make sure all information is accurate and complete. Some sections will ask for details on income, expenses and any tax adjustments, so be upfront and truthful. 

Step 4: Review and check before submission

Before submitting the CT600 form, double-check all entries for accuracy. However minor, a mistake can lead to delays and even potential penalties. 

Step 5: Pay your Corporation Tax

After submitting your CT600 form, pay your Corporation Tax on the UK government website. Remember, the due date is nine months and one day after the end of your company’s accounting period, so make sure that the payment is made by then to avoid any interest charges. 

Get in touch with us for help

Don't hesitate to get in touch with us if you need help completing your CT600 form, or for anything else regarding your company’s tax affairs. It takes less than a minute to submit an enquiry form, and we’ll get back to you to discuss what you need as soon as we can. 

CT600 form - FAQs

How do I get a copy of my CT600?

You can download the CT600 form from the HMRC website. And remember, after you submit the form, you should keep a copy for your records. 

Do I need an accountant to submit Corporation Tax?

While it's not legally required to hire an accountant, having the help of a certified professional can ensure everything is correct, particularly in complex financial situations. 

How long does it take to file a CT600?

The time it takes to complete and file a CT600 form will depend on how complex your company's finances are. Even if they’re relatively straightforward, it’s important to get together all the information you need before you start. 

Can you claim Corporation Tax back?

In some cases, you can claim relief and deductions that reduce your Corporation Tax bill. For example, you might be eligible for Research and Development (R&D) tax relief or be able to use losses from previous years to lower your current tax liability.