[jjgreen]

That depends on where you are. In the UK, while any debt can be paid in cash by law, there is no requirement for a business to refuse to accept cash for a purchase. There are some places that don't accept cash, some coffee shops, most cinemas: I guess that's more because they expect their staff to pilfer. Personally, I just don't use those places.

[HPsquared]

For anyone interested, that's the definition of legal tender: something which must be accepted as a payment method if offered for repayment of a debt.