What words are required by law to be on all US coins and paper currency?

in god we trust

More informationIn accordance with 31 U.S.C. § 5112, (d)(1): United States coins shall have the inscription "In God We Trust". The obverse side of each coin shall have the inscription "Liberty". The reverse side of each coin shall have the inscriptions "United States of America" and "E Pluribus Unum" and a designation of the value of the coin. The design on the reverse side of the dollar, half dollar, and quarter dollar is an eagle.

Note that Congress suspended the requirement for an eagle to appear on the back of the quarter for the duration of the State and National Monuments series. It was also deemed that the Statue of Liberty on the reverse of Presidential dollars was a suitable substitute for the Word Liberty on the obverse.