Export sales made 4 years before become bad debth

( Company) Client made export credit sale without ECGS scheme

1.After 4 Yrs amount not recovered and treated it as Bad debth

Bad debth a/c  Dr 

To Debtor a/c

2. My Doubt is whether he get any IT claim as once this Huge Sale amount is shown as revenue

Kindly Guide me with respect to AS conformity and IT aspect for this export sales?