If you run a UK limited company, you may need to file a Company Tax Return with HMRC. The return reports the company’s Corporation Tax position and normally includes the CT600 form, company accounts, tax computations and any relevant supplementary information.
Filing a Company Tax Return is separate from filing annual accounts with Companies House, and the Corporation Tax payment deadline is normally earlier than the Company Tax Return filing deadline.
This guide explains how to file a Company Tax Return, who needs to submit one, what information is required, the filing and payment deadlines, the software rules that apply from April 2026 and what happens if a return is late.
If you would prefer professional support, our Company Tax Return services can help with CT600 preparation, tax computations and HMRC submission.
What Is a Company Tax Return?
A Company Tax Return is the submission made to HMRC to report a company’s taxable profits, Corporation Tax calculation and other relevant information for an accounting period.
The CT600 is the main form within the Company Tax Return, but the CT600 is not necessarily the entire submission.
- Completed CT600 form
- Relevant CT600 supplementary pages, where required
- Company accounts
- Tax computations showing how taxable profits were calculated
- Other supporting information, where required
Who Needs to File a Company Tax Return?
A company or organisation must file a Company Tax Return if HMRC sends it a Notice to Deliver a Company Tax Return. The notice is commonly issued using form CT603.
You must still submit the return if the company made a loss or has no Corporation Tax to pay for the period.
If a company becomes liable for Corporation Tax but HMRC has not issued a notice, separate notification requirements can apply.
Do Sole Traders, Partnerships or Dormant Companies File Company Tax Returns?
Sole traders do not file Company Tax Returns. They normally report their business income through Self Assessment where a filing requirement applies.
Ordinary business partnerships do not file a Company Tax Return simply because they operate a business. A partnership normally has its own Partnership Tax Return, while the individual partners report their respective shares through Self Assessment.
Dormant companies require more care. If HMRC has already issued a Notice to Deliver a Company Tax Return, the company may still need to submit a return showing that it was dormant for that period.
Once HMRC has been told that a limited company is dormant for Corporation Tax, it normally does not need to file further Company Tax Returns unless HMRC sends another Notice to Deliver.
Being dormant for Corporation Tax does not automatically remove Companies House obligations. A dormant company can still have annual accounts and confirmation-statement requirements.
What Do You Need to File a Company Tax Return?
The exact information required depends on the company and its tax position, but a Company Tax Return normally brings together the company’s accounts and the tax calculations needed to determine its Corporation Tax position.
You will normally need the company’s identifying information, Corporation Tax accounting period, Company Unique Taxpayer Reference, statutory accounts, detailed tax computations and the appropriate CT600 information.
Supplementary CT600 pages may also be required in particular circumstances, including matters such as loans to participators in close companies, groups and consortium relief, controlled foreign companies and other specialist areas.
The taxable profit reported for Corporation Tax purposes can differ from the accounting profit shown in the statutory accounts because tax adjustments, allowances, reliefs and other Corporation Tax rules may apply.
For online filing, tax computations must normally be submitted in iXBRL format, and company accounts forming part of the return are also generally required in iXBRL for companies incorporated under the Companies Acts.
Need help with Corporation Tax calculations?
How to File a Company Tax Return Online
Company Tax Returns are normally filed electronically with HMRC.
HMRC’s former joint service for filing company accounts and Company Tax Returns closed on 31 March 2026. From 1 April 2026, companies generally need to use commercial software to file their Company Tax Return with HMRC.
The software needs to support the CT600 and the required accounts and tax computations. Companies House accounts remain a separate filing obligation, although some commercial software can support both processes.
A paper Company Tax Return is generally only permitted where you have a reasonable excuse for being unable to file online or where the return is being filed in Welsh.
Is a Company Tax Return the Same as Companies House Accounts?
No. They are related but separate filings.
A Company Tax Return is submitted to HMRC for Corporation Tax purposes. Annual statutory accounts are filed with Companies House.
Company accounts are also normally included as part of the information supporting the Company Tax Return submitted to HMRC, but submitting one filing does not automatically mean every other company filing obligation has been satisfied.
This distinction matters because Companies House accounts, Corporation Tax payment and the Company Tax Return can all have different deadlines.
Company Tax Return and Corporation Tax Deadlines
The Company Tax Return deadline and Corporation Tax payment deadline are different.
Company Tax Return: normally due 12 months after the end of the Corporation Tax accounting period.
Corporation Tax payment: normally due 9 months and 1 day after the end of the accounting period for companies that are not required to pay by instalments.
Larger companies can be subject to quarterly instalment payment rules, so the normal 9-month-and-1-day payment deadline does not apply in every case.
A Corporation Tax accounting period cannot normally be longer than 12 months. This means a company’s first set of accounts can sometimes require two Company Tax Returns where the accounts cover more than 12 months.
What Happens If a Company Tax Return Is Late?
| Delay | Standard consequence for filing dates on/after 1 April 2026 |
|---|---|
| Up to 3 months late | £200 flat-rate penalty |
| More than 3 months late | Flat-rate penalties total £400 |
| 6 months late | HMRC can make a tax determination and add 10% of unpaid Corporation Tax |
| 12 months late | A further 10% of unpaid Corporation Tax can apply |
Higher flat-rate penalties apply where Company Tax Returns are filed late for consecutive accounting periods. For the third and successive consecutive failures, the flat-rate penalty can rise to £1,000 where the return is up to three months late and £2,000 where it is more than three months late.
Late payment of Corporation Tax can also result in interest. That is separate from the penalty for filing the Company Tax Return late.
Read: Corporation Tax penalties from April 2026
Can You Amend a Company Tax Return?
Yes. If you discover that a Company Tax Return is incorrect after filing, you can normally amend the return.
HMRC says amendments must usually be made within 12 months of the filing deadline.
Errors should be corrected promptly because an incorrect return can affect the company’s Corporation Tax liability and may have penalty implications depending on the circumstances.
How Much Corporation Tax Will the Company Pay?
The amount of Corporation Tax due depends on the company’s taxable profits and circumstances. The Company Tax Return contains the Corporation Tax calculation, but detailed rates and marginal-relief guidance are better considered separately.
Read: How much is Corporation Tax for a limited company?
Frequently Asked Questions About Company Tax Returns
Is a CT600 the same as a Company Tax Return?
The CT600 is the main form within a Company Tax Return. The complete Company Tax Return can also include company accounts, tax computations and relevant supplementary pages.
Does every limited company need to file a Company Tax Return?
A company must file a Company Tax Return where HMRC has issued a Notice to Deliver one. A return is still required where the company made a loss or has no Corporation Tax to pay for that period.
When is a Company Tax Return due?
The normal filing deadline is 12 months after the end of the Corporation Tax accounting period. Corporation Tax itself is normally payable earlier, usually 9 months and 1 day after the end of the accounting period.
Can a dormant company need to file a Company Tax Return?
Yes. If HMRC has already issued a Notice to Deliver a Company Tax Return, a dormant company may still need to submit the return for that period. Once HMRC has been informed that the company is dormant, further returns are normally not required unless HMRC issues another notice.
Can you file a Company Tax Return on paper?
Generally only in limited circumstances, such as where there is a reasonable excuse for being unable to file online or where the return is being filed in Welsh.
Can a Company Tax Return be corrected after submission?
Yes. A Company Tax Return can normally be amended within 12 months of the filing deadline.
Get Help Filing Your Company Tax Return
Preparing a Company Tax Return involves more than completing the CT600. The figures need to agree with the company’s accounts, appropriate Corporation Tax adjustments must be made, and the correct computations and supporting information must be submitted to HMRC.
Accounting People can prepare the Company Tax Return, CT600, tax computations and relevant supporting schedules and handle electronic submission to HMRC.
If you need wider advice on Corporation Tax planning, reliefs or calculating your Corporation Tax liability, our broader Corporation Tax service can also help.
