I see three things that money says printed on it.
1) It says “This note is legal tender for all debts, public and private.” This means that anyone who puts something up for sale must accept the money. If the seller refuses to accept the money, a court of law would find the item as belonging to the buyer. The seller would forfeit the item for refusing to accept the money. This statement also says implicitly that the government has the sovereign right to make the money legal tender. You see this power implied by most of the other words on the U.S. dollar bill which constitutes the second thing I see money saying.
2) The dollar bill says that the money is issued by the United States of America. It repeats this authority with the picture of George Washington, signatures by the Treasurer and Secretary of the Treasury of the United States, pictures of the Great Seal of the United States on the back of the dollar bill.
3) It also says when and where it was issued (The dollar I have says it was issued by the Federal Reserve Bank of Boston as part of the 2006 series) and it says that this particular bill is number A 82297357D.
These three things all together say that this particular dollar bill is a genuine one and must be accepted because the United States government requires it to be accepted.
The legal nature of the dollar is pretty much ignored by economists as far as I know. They like to say that money is accepted because people have confidence in it. This neglect reflects a general anti-government bias. Free market neo-liberal economists like to think that the economy would run fine if government just stayed out of the way. Not so. Government sanction is essential to the acceptance of money.
Perhaps more interesting is what the dollar bill does not say. That will be my next blog.