Is there anything in the law about writing on notes? I was thinking about putting something like, join cointalk forum or something for some of the other forums I'm on and then spending them for free advertising for the forums I am a member of, and to try and generate interest in the different hobbies I have.
This is what the now AI-powered Internet had to say. I don't know how much the second bullet point applies to this situation. It is generally not illegal to write, doodle, or stamp on U.S. currency. However, it crosses into illegal territory under Title 18, Section 333 of the United States Code if you: Have the intent to render the bill unfit to be reissued (e.g., destroying, heavily mutilating, or completely coloring over it). Add commercial advertisements or business notices (prohibited by 18 USC 475). Alter the denomination of the bill to deceive someone (a form of fraud/counterfeiting). I will just add that I personally don't like writing/stamping on circulating currency. But that's just me.
Have you ever heard of the Where's George tracking website? A bunch of $1.00 bills were stamped with information you can use to put in the serial number and you can see where it has traveled throughout the United States. It's been ongoing for several years. I have put in at least 2 serial numbers I have found in circulation and have seen the different locations.
18 USC 475 says: This was passed in 1948, amended to include coins in 1951. It supersedes an earlier law from 1909 with similar verbiage, which as a non-lawyer I'm not qualified to interpret. So older coins counterstamped by businesses would have predated this. So I'm not sure it's technically legal to do what you suggest. It's unlikely anyone would make trouble about it - but if they did, that trouble would land on Peter (the owner of the site), and not the person who marked up the bills. For that reason alone, I'd choose not to do it.
Back in 1980, I ordered a rubber stamp with "IRAN LET OUR PEOPLE GO!" I stamped and circulated hundreds of bills over the next few months. I wonder if any are still around.
