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The $10,000 bill is the most valuable U.S. currency now in circulation, according to the U.S. Department of the Treasury.

The Treasury stopped printing it, along with the $500, $1,000 and $5,000 denominations, during World War II, and all such bills were declared obsolete on July 14, 1969. Today, Federal Reserve Banks destroy these notes when they receive them, but they remain legal tender while in circulation.

The $10,000 bill is also the most valuable circulating global currency, according to Roberto Cacciamani, former director of the International Bank Note Society. Tied for second place are the 10,000 SGD (Singapore dollar) note and the 10,000 BND (Brunei dollar) note, each equal to around $7,400 as of this writing, according to rates provided by Citibank N.A. via the Google Currency Convertor.

Runners-up include the 500 LVL (Latvian lats) and 1,000 CHF (Swiss franc) notes, each worth around $1,000.

Higher denominations exist as limited-edition commemorative notes issued to honor important persons or events, but because they are not circulating, they are not considered currency, according to Cacciamani. If Thailand's 500,000-bhat commemorative note were a circulating currency, it would take the prize as the most valuable piece of legal tender in the world its value is about $15,600.

Along similar lines, the most valuable U.S. note ever produced was the $100,000 gold certificate, only 42,000 of which were printed during their Dec. 18, 1934, through Jan. 9, 1935 run, according to the Treasury Department.

But the certificates were never in public circulation the Treasury Department issued them solely to Federal Reserve Banks, which used them only for transactions with one another. This practice continued until the early 1960s, when the government destroyed all but a few, which are now held by the Federal Reserve Bank of San Francisco, the Bureau of Engraving and Printing and the Smithsonian Institute.

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