Sale of

One of my friends is Central Government Employee filed his IT Return for the Assessment Year 2022--23 on the basis of his Form-16 and the IT Return was processed. Today he informed me that he sold his Right in the Joint Property for Rs.19,70,000 on 22-03-2022 (Financial Year 2021-22). The Capital Gain arising from this transaction was not shown in the IT Return. Till today there is no intimation from the IT Department. What is the solution for this? Can he now file Rectification? Please guide me.