What is a CT600?
A CT600 is the Corporation Tax return form that forms part of a company's Company Tax Return to HMRC. It sets out the company's Corporation Tax calculation for an accounting period, alongside the company's statutory accounts and supporting tax computations.
Who needs to file a CT600?
Any company that receives a notice from HMRC to deliver a Company Tax Return must file a CT600, even if the company has made a loss or has no Corporation Tax to pay. The return, accounts and computations are normally due 12 months after the end of the accounting period, while any Corporation Tax owed is normally due nine months and one day after the period end.
CT600 vs company accounts
This distinction is something founders regularly misunderstand. Company accounts report the company's financial performance and financial position, prepared under accounting standards. The CT600 and Company Tax Return instead report the information HMRC needs to establish the company's Corporation Tax position, built from the accounts but adjusted for tax purposes.
What information does a CT600 require?
A CT600 draws on the company's turnover, profit and loss account, balance sheet, and tax computations showing adjustments such as disallowed expenses, capital allowances and any reliefs claimed, including R&D tax relief where relevant.
Amendments and penalties
A CT600 can usually be amended within 12 months of the filing deadline. Late filing can trigger automatic penalties, which increase the longer a return remains outstanding, so keeping track of deadlines matters even where no tax is due.
Related terms: Corporation Tax, Corporation Tax Rate, Marginal Relief, Capital Allowances, Allowable Expenses.
Tax rules depend on individual circumstances and can change. This glossary is general information rather than personalised tax advice.