If the consumer pays by credit/debit card or cheque, the money is in the records and the merchants have to pay tax and there is no way they can avoid for a transaction paid by credit/debit card or cheque. If the consumer pays it by cash, the merchants have the flexibility to manipulate the exact amount they show for that transaction. This was the merchant can avoid paying tax completely or partially. Obviously the merchant cannot say this hidden agenda to the consumer. So they indirectly make the consumer pay by cash by saying that there will be additional some % charge if paid by credit/debit card or cheque.
