You may check CBP web site for detail.
wVEm:/;z& xa <UM5eI http://www.cbp.gov n=y[CKS vUohtS* The following is mentioned in U.S. Customs and Border Protection Declaration Form
[_1G@S6Ex `< xn8h9p Money And Other Monetary
_*1`@ Instruments
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RyjF~[e You may bring into or take out of the country, including
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UC by mail, as much money as you wish. However, if
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it is more than $10,000, you will need to report it to
<Bw^!.jAF CBP. Ask the CBP officer for the Currency Reporting
9f&C Form (FinCen 105). The penalties for non-compliance
3E!|<q$z can be severe.
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:vr “Money” means monetary instruments and includes U.S.
"nw;NIp! or foreign coins currently in circulation, currency, travelers’
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4@ checks in any form, money orders, and negotiable
C-\S/yd instruments or investment securities in bearer form.