EM8025 - Companies: Rights and Obligations: Amending a Return
FA98/SCH18/PARA 15
A company can amend its return within 12 months of the filing date, CTM93040 and CTM93300+. Where the time limit has passed a company can only amend the company tax return on completion of an enquiry to give effect to the conclusions stated in the closure notice and their consequences EM3870. HMRC can make jeopardy amendments during an enquiry EM1950+.
A company tax return that contains an inaccuracy which was neither deliberate nor careless at the time the document was sent to us will be treated as careless and a penalty due if the company discovers the inaccuracy at a later time and does not take reasonable steps to tell us about it, see CH81080.
The company should amend its return where the time limit for doing so has not passed or provide HMRC with details of the error so that it can determine whether a discovery assessment should be made.