A company tax return reports a company’s taxable profits and corporation tax position to HMRC. Most active UK limited companies need to file one for each relevant corporation tax accounting period.

A complete company tax return normally includes the CT600 form, company accounts, tax computations and any required supplementary pages. These documents explain how the company’s accounting results lead to its final corporate tax liability.

Company tax filing rules changed in 2026. HMRC’s joint online filing service closed on 31 March 2026. Companies now generally need compatible commercial software to submit their company tax return electronically.

Understanding the process helps directors meet UK company tax obligations and avoid unnecessary penalties. It also creates a clear link between bookkeeping, annual accounts, taxable profits and Corporation Tax.

What is a company tax return?

A company tax return is a formal submission that reports a company’s corporation tax position to HMRC. HMRC normally requires one after issuing a notice to deliver a return. The return covers a specific corporation tax accounting period. It reports taxable profits, tax adjustments, reliefs and the corporation tax due.

A complete return contains more than one form. It normally includes the CT600, relevant supplementary pages, company accounts and corporation tax computations. The annual accounts provide the financial starting point. They show the company’s income, expenses, assets, liabilities and accounting profit or loss. The tax computation then converts the accounting result into a taxable result. UK tax rules treat some transactions differently from accounting rules.

For example, certain expenses may appear in the accounts but receive no corporation tax deduction. Other expenditure may qualify for capital allowances instead of accounting for depreciation. The CT600 uses these adjusted figures to report the final company tax position.

How Do You Prepare a Company Tax Return?

You prepare a company tax return by completing the accounts, calculating tax adjustments and submitting the CT600 with supporting information. Good preparation starts with accurate bookkeeping. First, reconcile the company’s bank accounts against its accounting records. Check for missing transactions, duplicated entries, and unexplained balances. Next, review sales invoices, supplier bills, payroll records, and business expenses. Make sure the accounting records cover the correct financial period. Then prepare the annual company accounts. These financial statements establish the company’s accounting profit or loss. The next stage involves reviewing that profit for corporation tax purposes. Some accounting expenses qualify for tax relief.

For example, business expenses generally need to meet the relevant tax rules before reducing taxable profits. Certain entertaining costs and other non-deductible items can require an add-back. Accounting depreciation also normally requires adjustment for corporation tax. A company may instead claim capital allowances on qualifying assets.

What information goes in a company tax return?

A company tax return includes company details, financial information, taxable profits and the corporation tax calculation. The exact information depends on the company’s circumstances.

A typical return contains the company’s name, registration details and corporation tax accounting period. It also includes figures relating to profits, losses and tax payable. The company’s Unique Taxpayer Reference, commonly called a company UTR, identifies the business within HMRC’s tax system.

The filing package normally includes the CT600 form, annual accounts and tax computations. Additional CT600 supplementary pages apply where specific circumstances require them. The tax computation provides an important bridge between financial statements and taxation.

A simplified calculation is:

• Accounting profit: £50,000.
• Add non-deductible expenditure: £2,000.
• Deduct capital allowances: £4,000.
• Taxable profit before other adjustments: £48,000.
• Real company tax calculations may involve additional reliefs, losses or adjustments.

This example shows why accounting profit and taxable profit should not be treated as identical figures. Companies also need adequate company tax records to support their returns. These records include invoices, receipts, bank statements and accounting reports.

How to File a Company Tax Return in the UK?

UK company normally files its company tax return electronically with HMRC using compatible commercial software. The filing system changed from 1 April 2026.HMRC closed its former online service on 31 March 2026. Companies that previously used the service now generally need recognised commercial software for company tax return filing. The software prepares the electronic submission and sends the required information to HMRC. Online returns normally include accounts and tax computations in the required electronic format. HMRC uses iXBRL formatting for relevant online accounts and computations. Before filing, check that the accounts, tax computation and CT600 contain consistent figures. A successful online submission normally generates confirmation.

Do you file a company tax return with HMRC or Companies House?

A company tax return is filed with HM Revenue & Customs (HMRC), not Companies House. It is used to report your company’s taxable profits and work out how much Corporation Tax the company needs to pay. A company tax return normally includes the CT600 form, the company’s annual accounts, and supporting tax calculations. These documents provide HMRC with the information needed to assess the company’s income, expenses, profits, losses, and Corporation Tax liability.

Companies House has a different role. UK limited companies normally file their annual statutory accounts with Companies House. These accounts provide information about the company’s financial position and become part of the company’s public record.

This means that a limited company may need to send financial information to both organisations:

• HMRC: Company Tax Return (CT600), tax calculations, and accounts.
• Companies House: Annual statutory accounts and other company information.

From 1 April 2026, companies generally need to use commercial software to file company tax returns with HMRC because the previous joint online filing service closed on 31 March 2026. Keeping these two filing requirements separate helps businesses meet their UK tax and company reporting responsibilities.

Can you file a company tax return online?

Yes, Companies normally file company tax returns electronically using recognised commercial software. HMRC provides a list of commercial software suppliers that support Corporation Tax submissions. The previous HMRC joint online service no longer operates. It closed on 31 March 2026. Paper Company Tax Returns are now limited to specific circumstances.HMRC allows paper filing where a company cannot file online because of a reasonable excuse. Paper filing can also apply when submitting the return in Welsh. Most companies, therefore, need suitable software or an accountant with corporation tax filing software.

What Is Form CT600?

Form CT600 is the main corporation tax form within a UK company tax return. It records important information about the company and its corporation tax calculation. The CT600 reports figures such as taxable profits and Corporation Tax payable. It also identifies the accounting period covered by the submission. A tax computation supports these figures. It explains how information within the company accounts reaches the amounts reported in the return. Some companies require additional supplementary forms.

The necessary supplementary pages depend on the company’s transactions and tax circumstances. The CT600 therefore works as part of a wider filing package rather than as a standalone financial document.

Is CT600 the Same as a Company Tax Return?

No, the CT600 forms part of a company tax return, but the complete return contains additional documents. The distinction often confuses people. People commonly use “CT600” and “Company Tax Return” interchangeably. The complete tax submission normally includes the CT600, company accounts, and tax computations. Relevant supplementary pages can also form part of the return. 

The CT600 reports key tax figures. The company accounts explain the financial results. The tax computation explains how accounting profit becomes taxable profit. These documents give HMRC a complete picture of the company’s corporation tax position.

Can you file ct600 without software?

Companies normally need compatible commercial software to file a CT600 electronically. HMRC closed its previous Company Tax Return online service on 31 March 2026. Commercial software now provides the standard electronic filing route. Recognised software can prepare and submit the CT600 alongside the required accounts and computations.

Paper filing remains available only in limited circumstances, such as an accepted reasonable excuse or filing in Welsh. A business can prepare its accounting figures itself. Tax adjustments can become complex. Professional support can be useful when the company has losses, capital allowances or unusual transactions.

Who Needs to File a Company Tax Return?

A company or organisation generally needs to file a company tax return with HMRC when HMRC sends a notice to deliver one. This requirement usually applies to UK limited companies that are active for corporation tax purposes.

A company may be considered active if it is carrying on business activities such as selling goods or services, receiving income, making investments, or earning taxable profits. Corporation Tax can apply to profits from trading, investments, and the sale of certain assets.

You may need to file a company tax return even if the company:

• made a loss during the accounting period.
• has no Corporation Tax to pay.
• stopped trading during the year.
• was dormant for part of the period.

Receiving a notice from HMRC is important. If HMRC has issued a notice to deliver a company tax return, the company normally needs to submit the return even when no tax is due.

Dormant companies are treated differently. Once HMRC has been told that a company is dormant for corporation tax, it normally does not need to file further company tax returns unless HMRC asks for one or the company starts trading again.

Therefore, company directors should check both the company’s trading status and any notices received from HMRC before deciding whether a return is required

Do limited companies need to file a company tax return?

Active UK limited companies generally need to file company tax returns for their Corporation Tax accounting periods. The company remains separate from its directors and shareholders for tax purposes. Its profits therefore belong to the company before any later salary, dividend or distribution treatment. A limited company normally prepares annual accounts and a Corporation Tax return. An accounting period for Corporation Tax cannot normally exceed 12 months. This matters when company accounts cover more than 12 months.

For example, a company’s first set of accounts can cover longer than one year. That period may require two separate Company Tax Returns. Directors need to check the exact Corporation Tax accounting dates rather than relying only on the Companies House year-end.

Do dormant companies need to file a company tax return?

A dormant company usually does not need ongoing Company Tax Returns once HMRC accepts it as dormant. Dormant status for corporation tax differs from simply making no profit. A company may trade and make a loss. That does not make it dormant. A dormant company generally has no significant accounting transactions for the relevant period.

HMRC may still require action if it previously issued a notice to deliver a company tax return. The company should deal with that notice rather than simply ignore it. Dormancy also does not usually remove Companies House obligations.

A dormant limited company normally continues filing dormant company accounts with Companies House. The distinction is important; HMRC deals with corporation tax status. Companies House deals with statutory company filing.

Is a company tax return the same as a corporation tax return?

Yes, in the UK, ‘company tax return’ and ‘corporation tax return’ are often used to mean the same thing. The official HMRC term is Company Tax Return.

A Company Tax Return is submitted to HMRC to report a company’s taxable income, profits, losses, expenses, and Corporation Tax calculation. The main form used is called CT600.

The return normally includes:

• The completed CT600 form.
• The company’s annual accounts.
• Corporation Tax calculations.
• Any additional supporting information required by HMRC.

People often call it a ‘corporation tax return’ because the return is used to calculate and report Corporation Tax. However, HMRC generally refers to the complete submission as a company tax return.

For example, if a limited company earns taxable profits during its accounting period, it calculates the corporation tax due and reports the figures to HMRC through its company tax return.

What is the difference between company accounts and a company tax return?

Company accounts report financial performance, while a Company Tax Return reports the company’s Corporation Tax position. Company accounts include financial information about the business.

Depending on the reporting framework and company size, they can contain a balance sheet, profit and loss information, notes, and other required statements. The Company Tax Return uses figures from those accounts for tax purposes. The tax computation then adjusts the accounting result. For example, company accounts might contain £10,000 of accounting depreciation.

Corporation Tax calculations generally add back accounting depreciation. Capital allowances may then apply to qualifying expenditure. This difference explains why the profit shown in the accounts can differ from taxable profits. The documents also go to different government bodies. Companies House receives statutory accounts. HMRC receives the company tax return.

Who Is Responsible for Submitting a Company’s Tax Return?

The company remains legally responsible for filing an accurate company tax return by the deadline. Directors manage this responsibility for a limited company. A company can appoint an accountant or tax adviser to prepare the return. The adviser can also calculate corporation tax and make the online submission.

Using an accountant does not remove the directors’ responsibility for providing accurate information. Directors should therefore review important figures before submission. Accurate bookkeeping throughout the year makes this process easier. Maintain clear records for sales, purchases, payroll, assets and bank transactions. Also retain supporting documents for tax claims and adjustments. Poor records can cause incorrect company accounts. Those errors can then flow into the tax computation and CT600.

When Are Company Tax Returns Due?

A company tax return is usually due 12 months after the end of the corporation tax accounting period, although special filing-date rules can apply. The corporation tax payment deadline normally comes earlier. For many companies, corporation tax becomes payable nine months and one day after the accounting period ends. Consider a company with an accounting period ending on 31 March. Its corporation tax payment will normally fall due on 1 January.

The company tax return will normally be due by 31 March. Companies House accounts have a separate filing deadline. This distinction makes deadline management important. Businesses should track the accounts deadline, company tax payment date and company tax return deadline individually. Different payment rules can apply to large companies and certain other businesses.

What are the penalties for filing a company tax return late?

HMRC charges penalties when a company tax return is filed after the statutory deadline. For returns with a filing date on or after 1 April 2026, the fixed late-filing penalty is £200. If the return remains outstanding for more than three months, the total fixed penalty increases to £400. A further tax-related penalty can apply when the return is more than six months late. HMRC can estimate the corporation tax due and charge 10% of the unpaid tax.

If the return remains outstanding for 12 months, HMRC can charge another 10% of the unpaid tax. This means tax-related penalties can reach 20% of unpaid corporation tax for prolonged delays. Repeated late filing can lead to higher fixed penalties. For a third or subsequent consecutive late return, the penalties can rise to £1,000 within three months and £2,000 after three months.