CTM95005 - Corporation Tax self-assessment (CTSA): Discovery Assessments and Determinations General

The self assessment contained in a company tax return creates a legal charge to tax. Subject to the right to make a discovery assessment or discovery determination the return is final once made, unless within the relevant time limits:

• the company amends it, see CTM93300 and COM23010 . (For GOV.UK users see COTAX manual.)
• an officer decides to enquire into it
• the conclusions stated at the end of an enquiry into a return for a different period require a consequential amendment to it (FA98/SCH18/PARA34 (2A)).

See the Enquiry Manual for guidance on opening and conducting enquiries.

You can find guidance about discovery assessments and discovery determinations in the Enquiry Manual, see EM3200+.