C form not received

if seller do not file C form then  he would have to pay tax at normal tax applicable as if goods are not sold inter state 

At at time of Assessment normal after 2 & half year Seller hv to pay CST as per the Applicable Rate of Vat in concerned State with Interest on from the date of due date of payment to the Assessment Order.

So, Its better Seller pay the Extra Taxes * suppose Applicable Vat Rate is 14.5% - 2% = 12.5% as outstanding CST to avoid Interest.