"Here it is. Secretary Jack Lew's official #signature as it will appear on U.S. currency starting this fall," the tweet said, accompanied by a picture of Lew's signature.
The signature will be on newly printed bills, beginning with the $5 bill this fall.
When the bills actually enter circulation depends on when the Federal Reserve releases currency, Politico reported. As the Fed orders replenishment bills, eventually all U.S. bills will carry Lew's signature.
The Treasury's website indicates an average of 35 million currency notes were printed daily in fiscal year 2012.
When he announced Lew's nomination, Obama said he'd asked Lew to "make at least one letter legible in order to not debase our currency should he be confirmed as secretary of the treasury."