NRE A/c

In a NRE account in Singapore which was in the name of Husband and Wife, the name of son who was Resident Indian was added after the death of his father. No transaction was done by him either of withdrawal or deposit by him from India however in the ITR the details of that account was not disclosed due to oversight. The account is closed now and all the payment was transferred in wife other account. Notice received from Income Tax department in favour of son under section 131(1A) . No records are available. please inform what reply to be given. if affadavit can work on this?