Legal tender is a quality given by government to certain forms of money such that a creditor who refuses to accept that money in payment of a debt loses certain rights (e.g. to collect further interest. In our system, federal reserve notes are legal tender,your personal check is not. It is acceptability, not government edict wich makes something money. (Note the development of NOW accounts, e.g.). Credit cards are not money. When you use a credit card, you are promising to pay in the future. The merchant sells this promise to the credit card issuer. In order for electronic money to be true cash, it must be able to circulate from Alice to Bob to Carl to Dave without the need to contact the issuing bank. Otherwise, it is merely an electronic check, perhaps anonymous. If Bob must deposit or validate the money first in order to make sure Alice doesn't double spend it, then it is no different from Alice having $200 in her checking account and writing a $150 check to Bob and a $150 check to Carl. The first one who gets it to her bank collects, the other one has it bounced back.