E1 from

My client has Purchase goods in RR Sales (In transit sales), he has sold the good to out state party, from whom they will get C FORM, Not they have to give C FORM to selling payrt and get E1 from therm, but the selling party from whom they have purchsased has defaulted and is not able to provide the E1 , what will be my party's liability and do they have to pay pentalty or tax.

State : GUJARAT