31 CFR 1010.311 : Money And Finance: Treasury (§ 0.101 To Parts 1061-1099) — (Part 500 To Parts 1061-1099) — Regulations Relating To Money And Finance (Continued) (Part 500 To Parts 1061-1099) — Financial Crimes Enforcement Network, Department Of The Treasury (Parts 1000-1009 To Parts 1061-1099) — General Provisions (§ 1010.100 To § 1010.980) — Reports Required To Be Made (§ 1010.300 To § 1010.370) — Filing obligations for reports of transactions in currency.

Each financial institution other than a casino shall file a report of each deposit, withdrawal, exchange of currency or other payment or transfer, by, through, or to such financial institution which involves a transaction in currency of more than $10,000, except as otherwise provided in this section. In the case of the U.S. Postal Service, the obligation contained in the preceding sentence shall not apply to payments or transfers made solely in connection with the purchase of postage or philatelic products.