What is a CT600 form?
Answered 11 March 2026
What is a CT600 Form?
HMRC Guidance / Practice
The CT600 is the Corporation Tax return form used by companies to report their tax position to HMRC.
A company is required to file a CT600 in response to a CT603 — a formal notice issued by HMRC's COTAX system requiring a company to make a return.
The CT600 is accompanied by a range of supplementary pages for specific circumstances, including:
| Form | Purpose |
|---|---|
| CT600A | Close company loans or arrangements to confer benefits on participators |
| CT600B | Controlled foreign companies and foreign permanent establishment exemptions |
| CT600C | Group and consortium relief |
| CT600D | Insurance |
| CT600E | Charities and Community Amateur Sports Clubs (CASCs) |
| CT600F | Tonnage Tax |
| CT600H | Cross-border Royalties |
| CT600I | Supplementary charge in respect of ring fenced trades |
| CT600J | Disclosure of tax avoidance schemes |
| CT600L | Research and Development |
| CT600M | Freeports and Investment Zones |
| CT600N | Residential Property Developer Tax |
Substitute versions of the CT600 (and its supplementary pages) are acceptable, provided HMRC has formally approved them. Approved substitutes must bear a unique identifier showing their origin.
If a company needs to amend a submitted CT600 (e.g. to correct a mistake), it must submit a completely new return covering all required information — not just the corrected figures.
Citation sources
The following forms are relevant to the company's obligation to comply with the requirements of a notice to deliver a return. Form Description CT114 Covering letter, available on SEES, to be used by the HM Revenue & Customs office when sending back an unsatisfactory return. CT208 Combined payment and return reminder issued by COTAX 42 days before the filing date if no payment has been received and no return has been logged for that AP. CT205 Return reminder issued by COTAX 42 days before the
Substitute versions of forms CT600 (and the supplementary return pages) are acceptable if HMRC has formally approved them. The (This content has been withheld because of exemptions in the Freedom of Information Act 2000) team deal with the approval of substitute forms. Approved substitute versions closely resemble the official forms, except that they are usually black on white. Any substitue form that’s centrally approved by that team must bear a unique identifier so that its origin can be ident
The form cannot be amended after it has been submitted, so users of the form should check their answers carefully every time the form shows a review page. A company may need to change a form, such as to correct a mistake or add a previously unincluded production. To do this, the company must fill out a new form to replace the original one. The new form must include all the information required for a complete claim, not just the information that is being corrected or added. If the company submit
The following forms are relevant to the handling of returns. Form Description CTSA214 Stock letter used by HMRC when sending back an unsatisfactory return. It is available on SEES. CT600 CT return form. CT600A CT600 return form supplementary page. Close company loans or arrangements to confer benefits on participators. CT600B CT600 return form supplementary page. Controlled foreign companies and foreign permanent establishment exemptions. CT600C CT600 return form supplementary page. Group and