In this case, Assessing Officer is of the opinion that ITR filed by the assessee is defective. The best part is that a proper error description is shared and the AO also suggests a probable solution to rectify the same. The assessee is given an opportunity to respond within 15 days from the date of intimation or before it is assessed. If you don’t respond within 15 days then your return will be rejected by the AO. The defect u/s 139(9) can be the wrong ITR filed, missing information, incomplete return, etc.