Verify Genuine VAT Collection

Dear Friends

Whenever we purchase anything from a small shop, or some small time dealer , company he puts VAT in his bill, but in the bill there is no legal registration number of anything, like CST, etc, VAT etc, my query is if someone bills you VAT in the bill how to confirm that he really will pay that VAT to govt, because there is possibility that he might charge VAT from us and not pay at all and not show the bill in his records,,,