If a common man who is ultimate consumer purchase from an unregistered seller, there be no tax liability on purchase.
Tax liability arises when either of the party is registered under GST.
For common man there is nothing he need to comply with GST. With a good civic sense he should demand a bill for each purchase.
chatCommentsWHAT WILL BE TAX LIABILITY IN CASE PURCHASE GOODS FROM REGISTERED DEALER - JANMEJAYA ROUTIn that case also common man don't have to do anything. Registered person will collect tax as charged in tax invoice and pay to government. - Pulkit SharmaHOW MANY COST TO A COMMON MAN IN CASE GOODS PURCHASED FROM REGISTERED DEALER & UNREGISTERED DEALER - JANMEJAYA ROUT