Filing a CT600 is one of the most important tax obligations for UK limited companies, and it can sometimes feel daunting. You must submit Form CT600 to HM Revenue and Customs (HMRC) if your company receives a Notice to Deliver a Company Tax Return (CT603), even if the company made little profit, made a loss, or was inactive during the accounting period.
This document declares the company’s income, allowable business expenses, and final Corporation Tax calculations. However, many business owners don’t know how to file CT600 company tax return UK.
This guide explains how you can file CT600 company tax returns in the UK, what documents you need, and how to complete an HMRC CT600 submission correctly. So, let’s get started.
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What Is a CT600 Company Tax Return?
A CT600 is the official Corporation Tax return UK document that companies must submit to HMRC. Even if a company made no profit or ran at a loss, it must still submit a CT600 if HMRC has notified it to deliver a company tax return.
Form CT600 reports company income, allowable business expenses, taxable profits, Corporation Tax due, and tax reliefs and adjustments. Additionally, the return is normally submitted electronically together with statutory accounts, tax computations, and iXBRL-tagged accounts.
Who Needs to File CT600 In the UK?
Before diving into how to file CT600 Company Tax Return UK, it is essential to learn who must file this document. Any UK company or unincorporated association that receives a Notice to Deliver a Company Tax Return (form CT603) from HMRC must submit a CT600 company tax return.
Keep in mind that, even if you made a loss during the accounting period, owe no Corporation Tax, or were dormant for part of the accounting period, you still need to submit it.
Sole traders and ordinary partnerships do not file CT600 returns. Instead, they normally report their business income through Self Assessment tax returns.
What You Need Before Your HMRC CT600 Submission?
If you are learning how to file CT600 company tax return UK, you need to gather the right information before you get started. Gathering the right information can help you avoid delays and filing errors.
HMRC Details
You will need your company’s Unique Taxpayer Reference (UTR), issued by HMRC when the company was registered for Corporation Tax. Also, you will need the company’s Government Gateway user ID and password.
Financial Documents
Do not forget your financial documents. Gather your company’s statutory accounts for the accounting period, and records of any capital allowances, reliefs, or tax credits being claimed. You will also need Corporation Tax computations showing how accounting profit is adjusted to calculate taxable profit.
Technical Requirements
Generally, HMRC requires accounts and tax computations submitted with a CT600 to be in iXBRL format.
Remember, having these details ready is one of the most important steps in understanding how to file CT600 company tax return UK efficiently.
How to File CT600 Company Tax Return UK? Step-By-Step Process
To understand how to file CT600 online, follow these steps:
Prepare Your Accounts
The very first step is to prepare and complete your statutory accounts for the relevant accounting period.
Calculate Taxable Profits
Adjust your accounting profit for disallowable expenses, losses, capital allowances, and other tax adjustments.
Use HMRC-Approved CT600 Software
Use HMRC-recognised Corporation Tax software, or accounting software that supports CT600 filing, such as an approved commercial tax software package. Many accountants also submit CT600 returns on behalf of clients.
Gather Company Information
Gather the essential company information, including the company UTR, Government Gateway credentials, Companies House registration number, and statutory accounts and financial records.
Calculate Taxable Profit
An essential step in how to file CT600 company tax return UK is calculating accurate taxable profit. Start with accounting profit, then add back disallowable expenses, and deduct capital allowances and other eligible tax reliefs.
Complete the CT600 Form
Enter company details, income, expenses, accounting period dates, and Corporation Tax calculations. You can complete and submit it using HMRC-recognised commercial software because HMRC’s free online CT600 filing service has been withdrawn.
Your chosen software will normally populate the relevant CT600 boxes for turnover, profits, taxable profit, expenses, and Corporation Tax due based on the information you enter.
Moreover, if your company receives certain types of income or wishes to claim specific reliefs, you may also need to submit supplementary pages.
Attach iXBRL Accounts and Tax Computations
The next crucial step in how to file CT600 company tax return UK is submitting accounts and computations. These must be submitted in a digital format called Inline eXtensible Business Reporting Language (iXBRL).
Usually, HMRC-recognised commercial filing software automatically converts your accounts and tax computations into iXBRL. Therefore, you usually do not need to add the digital tags manually.
Submit the Return Online
Once you complete your CT600 form and attach any supplementary pages, submit the HMRC CT600 and keep the electronic receipt as proof of filing.
Usually, HMRC requires almost all Company Tax Returns to be filed online. Paper filing is accepted only in some situations, such as when a company has a reasonable excuse preventing online filing, or when the return is submitted in Welsh.
What Is the CT600 Filing Deadline?
Now that you know how to file CT600 company tax return UK, let’s discuss its deadline. The dates for filing your paperwork and paying your tax bill are different. Both dates are important, so mark them clearly on your business calendar.
You must submit your completed CT600 return within 12 months after the end of your accounting period. You must pay your Corporation Tax bill within 9 months and 1 day after the end of your accounting period.
What Are the CT600 Penalties for Late Submission?
You will get penalties for missing the CT600 filing deadline. If the return is even one day late, HMRC normally charges an immediate £200 penalty. An additional £200 is charged when you are 3 months late.
Furthermore, if you are 6 months late, HMRC will estimate your Corporation Tax bill and add a penalty of 10% of the unpaid tax. Another 10% of any unpaid tax will be charged if you are 12 months late.
Can I File the CT600 Myself?
Learn how to file CT600 Company Tax Return UK, as this can help you understand the rules and file it yourself. In the UK, many company directors file their own CT600 without using an accountant.
If your company’s tax affairs are relatively simple, with no group relief, complex capital allowances, or associated companies, then the process is usually manageable. You just need HMRC-recognised CT600 software that can produce the required iXBRL accounts and tax computations, along with an understanding of your company’s accounting figures and the basic tax adjustments.
However, if your company has complex tax issues, or you don’t know how reliefs and allowances are claimed correctly, seek professional accounting or tax advice. A professional can help reduce the risk of filing errors.
Can I Pay Corporation Tax Before Filing?
Another important part of how to file CT600 company tax return UK is paying corporation tax. If you are wondering whether you can pay Corporation Tax before filing, the answer is yes. You can pay Corporation Tax before filing your CT600 return.
To Pay Corporation Tax, you should prepare your Corporation Tax calculations first so you know how much tax is due.
Since the payment deadline is earlier than the filing deadline, you need to calculate the estimated tax due, make the payment to HMRC, and then submit the CT600 return later.
How to File CT600 for a Dormant Company?
To understand how to file CT600 company tax return UK, you must learn how you can file when you are a dormant company.
To file a CT600 as a dormant company, first check whether HMRC has issued a CT603 and has not withdrawn it. If a return is required, prepare your company’s dormant statutory accounts that will show no trading income and no trading expenses.
Use CT600 online filing software to complete the return with the relevant dormant or zero figures. It will convert the accounts and tax computations into iXBRL format and submit the CT600 electronically to HMRC.
How to Amend a CT600 Return?
To amend a CT600 Company Tax Return, you must submit a corrected return electronically using HMRC-recognised commercial tax software. Well, a CT600 can normally be amended within 12 months of the statutory filing deadline.
Since HMRC no longer provides its own online CT600 filing service, amendments must generally be submitted using HMRC-recognised commercial software.
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The Bottom Line
Understanding how to file CT600 company tax return UK is important for every limited company in the UK. The process is generally straightforward for companies with simple tax affairs. You just need to prepare statutory accounts, calculate taxable profits, use CT600 online filing software, and complete an accurate HMRC CT600 submission before the deadline.
Follow the steps above and check your figures carefully to avoid unnecessary CT600 penalties. If your company has complex transactions or multiple income streams, professional accounting support can help ensure your CT600 is fully compliant and tax-efficient.
At CheapAccountantsInLondon, we help you with your Corporation tax return, annual tax return, and claim a refund for overpaid taxes. If your company is dormant, we can also help you with dormant company accounts while ensuring your business remains HMRC-compliant.
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