If any dealer faces the issue of “Signature validity is Unknown” in Digital Signature panel e-CST declarations issued online by MGSTD, please add the Certificate in Trusted certificate of your PDF viewer. Detailed steps to be followed are given in the manual “Validating e-CST Forms”. Path for it as MGSTD Portal>Dealer Services > Manuals and procedures> second page Sr.22 Others> Subject>Validating E-CST forms.