Someone in The BBQ Pit or Politics & Elections posted that U.S. currency notes must be signed by the Treasurer and the Secretary of the Treasury, and that if the President replaces the signature of the Treasurer, then the bill would not be legal tender. A cite (the law) was posted. Unfortunately, I cannot find the post; so I’ll ask here: Is the poster’s assessment valid? Or are the signatures of the two Treasury officials just traditional?
According to this NPR interview, it’s legal. That was the first question.
INSKEEP: OK. So sit - so on this $10 bill, it’ll be on the left-hand side, is where it would be. OK. And is this legal to put a sitting president’s signature on the currency?
MCLAUGHLIN: Yes. So as far as the Treasury Department is concerned, the changing of signatures is actually quite routine. It happens anytime there’s a change of administration, and the administration appoints a new treasurer and a new Treasury secretary. So it’s not actually something that requires congressional approval or the passage of a law. The notes are updated with new appointees in every run, so it’s up to the Treasury Department to make that call when the new signatures go on the notes.
INSKEEP: OK. But…
MCLAUGHLIN: It’s just unprecedented, yeah.
Though it’s legal, it is a total break with a tradition going back 165 years.
That discussion does not distinguish between the case of changing the person who’s in the role of Treasurer or SecTreas, versus changing which roles sign the bills.
Yes the former happens quite routinely, certainly at every change of administration and sometimes more than once during an administration. However the latter is the topic at issue. So the cite is not a definitive answer at all.
As far as I can tell, the only law on the design of paper currency is 31 U.S. Code § 5114(b), which says nothing about signatures:
(b) United States currency has the inscription “In God We Trust” in a place the Secretary decides is appropriate. Only the portrait of a deceased individual may appear on United States currency and securities. The name of the individual shall be inscribed below the portrait.
Edit: There are some other minor provisions for the design of Federal Reserve notes (which is all of them nowadays):
Federal Reserve notes shall bear upon their faces a distinctive letter and serial number which shall be assigned by the Board of Governors of the Federal Reserve System to each Federal Reserve bank.
And:
Such notes shall be in form and tenor as directed by the Secretary of the Treasury under the provisions of this chapter and shall bear the distinctive numbers of the several Federal reserve banks through which they are issued.
Nothing about signatures there either.
Once they stop just being cash money and turn into collectables, the official signatures are a main means of identifying and differentiating notes of particular denomination, and putting a label on those versions which might be rarer and worth a bit more.
Since they are issued by the authority of the government and the statutory reserve bank, then the design carries relevant secretary’s as the constitutional authority and bank governor’s signature as they guy responsible for making sure there is enough toner and fixing any paper jams. Its probably such a long-standing convention that most national statutes will not even have bothered to specify it in law.
That sounds definitive enough for me. Darn. Thank you.
Can someone tell Trump that he will need to personally sign every single banknote? Perhaps the tedium will discourage him.
Like I said above: autopen. Surely he’s not a hypocrite.
It all depends on whether or not the flag as gold trim or not. 
It is though. The relevant part is where it’s up to the Treasury Department to determine who signs it.
You can’t prove a negative, but the total lack of any evidence that there’s anything illegal should be fairly definitive.
I appreciate the humour, but I want to be clear that I started the thread for a factual answer.
Can the Treasury Department determine any given individual can sign them? ISTM that the signature certifies that the U.S. Treasury is responsible for the note’s value. If this certification is made by someone who is not in the Treasury Department, is the certification valid?
I only posted after the first three or four replies that seemed to offer the factual answer.
No worries. I just wanted to make sure it stayed somewhat on-track. 
Absence is not proof, but I can’t find any legitimate news sources questioning the legality of the act. The only comment I took seriously I traced back to an AP article, which other news outlets are quoting.
Michael Bordo, director of the Center for Monetary and Financial History at Rutgers, said the move will undoubtedly come with political pushback, “but I do not know if he has crossed any legal red lines” since the Treasury Secretary may have the authority to decide who signs the currency.
Of course, but it appears asked and answered.
It seems yes, because the Treasury Department has decided it is. It doesn’t matter whose signature is on them, as long as that signature is whatever the department decides it should be. Previous bills being signed by someone at the department are a matter of custom and tradition, and nothing more.
And even if it was illegal you know that would mean fuck all to this administration.
I think printing illegal money might at least be an inconvenience for them, but really it would be another thing to add to the pile.
If they give him a Sharpie he’ll be excited to sign every one….
Jimmy Kimmel showed a Trump Sharpie signature - which was scrawled across the entire front of the bill masking everything else. Just the way Trump would want.
On the subject of Sharpies, there’s this wonderful headline.