When you set up a limited company and begin trading, you have a legal obligation to prepare a Company Tax Return after the end of every ‘accounting period’ and deliver it to HMRC. This guide explains how to complete and submit a tax return, the information you need to include, and the filing deadline you must meet.
All companies in the UK must complete a Company Tax Return for HMRC at least once every 12 months if they are ‘active’ for Corporation Tax. To be able to do this, you must first register for Corporation Tax with HMRC.
The purpose of a return is to report the income, expenditure, profit or loss, and Corporation Tax liability of a company during a specified period of time, known as the ‘accounting period’.
A Company Tax Return consists of:
HMRC will send a ‘Notice to deliver a Company Tax Return’ to your registered office address to remind you that one is due. The filing deadline is normally 12 months after the end of your Corporation Tax accounting period.
You can complete the tax return yourself, or you can appoint an accountant to prepare and file it on your company’s behalf.
The key information that you must enter on form CT600 includes (but is not limited to) the following:
There are many other details that you may or may not have to include on form CT600 and the supplementary pages. It depends on your company’s particular activities. For full guidance on what to include, please refer to HMRC’s Company Tax Return guide .
The person who completes and files the Company Tax Return must include a declaration that, to the best of their knowledge and belief, the information they are providing is correct and complete. This is usually the director, company secretary, or accountant.
If you appoint a tax agent (e.g. an accountant) to complete and submit the tax return on your company’s behalf, the agent must complete the declaration.
However, if a tax agent is only responsible for submitting the return (rather than also completing it), the declaration must be made by an officer of the company (e.g. a director or company secretary) or another authorised person.
Your Company Tax Return must be accompanied by full (statutory) annual accounts . These accounts should include:
The financial year covered by the annual accounts is usually the same 12 months as the accounting period covered by the Company Tax Return. However, this may not be the case at the end of the company’s first year. We discuss this in more detail below.
Almost all companies are required to file their tax returns electronically using commercial third-party software that has passed HMRC’s testing procedures. Some commercial software listed enables you to file your tax return and annual accounts together.
In certain circumstances, a company may be exempt from electronic filing. You can complete and submit the paper form CT600 instead if you:
You will also need to include form WT1 to explain why you are using the paper form.
HMRC’s Company Taxation Manual COM60040: CT online filing provides more information on exemptions.
Your company’s accounting period for Corporation Tax determines the deadlines for filing your Company Tax Return and paying your Corporation Tax bill.
The ‘accounting period’ is the time covered by the Company Tax Return. It begins on the day that your company becomes ‘active’ for Corporation Tax (e.g. the day you start trading).
It cannot be longer than 12 months and it normally corresponds with the financial year covered by the annual accounts. HMRC will send a letter to your registered office address confirming your first accounting period when you register for Corporation Tax.
The deadline for filing your Company Tax Return is 12 months after the end of the accounting period for Corporation Tax.
For example, if your accounting period starts on 1 April 2026 and ends on 31 March 2027, you must deliver the Company Tax Return for that period by 31 March 2028.
Sometimes, a company’s accounting period for Corporation Tax may not be the same as its financial year. This is often the case in the first year of business.
Your very first annual accounts will probably cover more than 12 months. This is because your company’s financial year:
For example, if you were to set up a company on 1 April 2026, your accounting reference date would be 30 April 2027. Therefore, your company’s first financial year would run from 1 April 2026 until 30 April 2027, which is more than 12 months.
Since your accounting period cannot be longer than 12 months, you may have to complete two Company Tax Returns to cover the financial year in the first accounts.
It depends on whether you start trading on the day that you set up your company, or at a later date.
Let’s say that your company starts trading on the same day that it is set up. Using the example dates above, you would have to prepare:
In subsequent years, the 12-month accounting period covered by the Company Tax Return should align with the 12-month financial year covered by the annual accounts. This means that your company’s financial year and accounting period would be 1 May to 30 April from 2027 onward.
The deadline for paying your company’s Corporation Tax bill is 9 months and 1 day after the end of your accounting period.
For example, if your accounting period ends on 30 November, you must pay the Corporation Bill for that period by 1 September the following year.
However, you may have two payment deadlines for your first year in business. This will be the case if your first financial year is longer than 12 months, and you have to file two Company Tax Returns to cover that period of time.
Since Corporation Tax is due before the Company Tax Return filing deadline, you should prepare your tax return as soon as possible after the end of the accounting period.
HMRC will send you a Corporation Tax bill with the payment deadline and information on how to pay .
A range of different bodies are legally required to prepare a Company Tax Return for HMRC, including:
If you are a sole trader or in a business partnership, you do not send a Company Tax Return. Instead, you must send a Self Assessment return to HMRC every year.
If your company is dormant for Corporation Tax purposes, you do not have to complete a Company Tax Return or accounts for HMRC for as long as the company remains dormant. However, you must tell HMRC that your company is dormant, otherwise they may ask you to send a tax return.
A company may be dormant if it is:
If your company is new or has become dormant after previously trading, you must tell HMRC within 3 months, if and when you do start trading. To do so, you simply register for Corporation Tax online.
Whilst dormant companies do not have any filing obligations for HMRC, you will still need to prepare annual accounts and an annual confirmation statement for Companies House. You must also continue to maintain your company’s statutory registers and report any change of details to Companies House.
You must prepare a Company Tax Return even if your company makes a loss and/or you do not have any Corporation Tax to pay. HMRC still needs to know about your company’s income and expenditure, profits or losses, and the calculations and computations you used to work out your tax liability.
If you do not owe any Corporation Tax, you must notify HMRC by submitting the ‘nil to pay’ form . You should do this before filing your Company Tax Return, otherwise HMRC will send you payment reminders.
HMRC is very strict when it comes to filing and payment deadlines, so you must endeavour to prepare and file your Company Tax Return by the deadline – 12 months after the end of your company’s accounting period.
If you deliver your tax return late, the following late filing penalties will apply:
If you file your Company Tax Return late three times in a row, the £200 penalties will automatically increase to £1,000 each.
You can only appeal these penalties if you have a reasonable excuse. If you want to appeal, you must write to your company’s Corporation Tax office. You will find the address on any official letter you have received from HMRC, including the Notice to deliver a Company Tax Return.
You can usually make changes to a Company Tax Return up to 12 months after the filing deadline. You can do this in one of the following ways:
Contact HMRC’s Corporation Tax helpline if you have any questions about making changes to a tax return.
Limited company accounting and tax requirements can be time-consuming and particularly complex, more so if you do not have any relevant experience. Whilst you are allowed to prepare Company Tax Returns and accounts yourself, we would always recommend that you appoint an accountant to take care of these things for you.
This will ensure that your company finances and tax affairs are being expertly managed, and completed in accordance with the statutory requirements. A good accountant will also understand how to minimise your company’s expenditure and tax liability and help you grow and develop your business
You must tell HMRC if you appoint and authorise someone to deal with your company’s tax affairs. If you use an accountant, they will tell you how to do this.
Preparing a Company Tax Return for HMRC can be a challenging task, and it’s easy to make mistakes. Whilst HMRC provides comprehensive guidance, it makes sense to lighten the load by appointing an expert to take care of your tax returns and accounting needs.
We hope that this guide has explained the process involved in preparing and filing a Company Tax Return. If you have any questions or would like to speak to someone about setting up a limited company in the UK, please leave a comment below or get in touch with our team.