So I started looking into this, because it's interesting.

So, merchants can reject cash for purchases[1] because cash is legal tender for all debts, public charges, taxes, and dues, and a purchase is not one of these.

The Wikipedia page [2] for dining and dashing states that ordering a meal is a contract debt, since you are given the food before the transaction occurs, with the understanding that you'll pay for it afterwards. Thus, if the merchant, after giving you the food, informed you that they only accept credit card, that would not be allowed.

Also some good discussion on this SE post [3]

1. https://www.federalreserve.gov/faqs/currency_12772.htm 2. https://en.wikipedia.org/wiki/Dine_and_dash 3. http://skeptics.stackexchange.com/questions/7701/is-it-illeg...

It's completely true. If I finish my meal and don't have a credit card, the restaurant will be annoyed. I offer them cash, and they refuse the payment. I therefore leave without paying. The restaurant takes me to court for non-payment and I agree to pay. I pay in cash. From the link in your sibling comment:

"This statute means that all United States money as identified above are a valid and legal offer of payment for debts when tendered to a creditor"

Being a legal offer of payment is different from being mandated to accept that payment. You may be right, but I would find it surprising.

The normal interpretation is that the party you're paying doesn't have to accept, but has no legal standing to say "You owe me and didn't pay".