As of today, it is illegal for a merchant to refuse cash. Not saying what the future may bring, though, since credit cards are already accepted by fu@@ing parking meters, even. Soon, pay toilets?
It’s unlawful to refuse federal reserve notes as a discharge instrument for a debt. You can refuse to take them in a transaction all day long.
Sorry, but that’s not quite true.
Is it legal for a business in the United States to refuse cash as a form of payment?
Section 31 U.S.C. 5103, entitled “Legal tender,” states: “United States coins and currency [including Federal reserve notes and circulating notes of Federal reserve banks and national banks] are legal tender for all debts, public charges, taxes, and dues.”
This statute means that all United States money as identified above is a valid and legal offer of payment for debts when tendered to a creditor. There is, however, no Federal statute mandating that a private business, a person, or an organization must accept currency or coins as payment for goods or services. Private businesses are free to develop their own policies on whether to accept cash unless there is a state law which says otherwise.
https://www.federalreserve.gov/faqs/currency_12772.htm