Doesn’t federal law require that you must accept U.S. currency?
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
Cash has to be honored for debts. When you want to buy something, there is no debt, so no, a merchant doesn’t have to accept currency. Of course you are under no obligation to patronize such a merchant.
Allegiant Airlines won’t accept cash on board. Only debit and credit cards.
It is probably more correct to say that the federal government guarantees the dollar value of the currency. There are many cashless businesses.