From the
USPS:
1.2 Purchase Restrictions
A postal customer may buy multiple money orders at the same time, in the same or differing amounts, subject to these restrictions:
a. The maximum amount of any single money order is $700.
b. Without exception, no customer may buy money orders on any 1 day whose total value exceeds $10,000. This daily limit applies regardless of the number of visits made by a customer to one or more postal facilities.
c. Any customer whose daily total of purchased money orders is from $3,000 to $10,000, inclusive, must also complete Form 8105-A and show identification bearing the purchaser?s photograph, name, and address.
1.3 Purchase Method
Money orders must be paid for in one of these ways:
a. In U.S. currency and coins (in any amount).
b. With established traveler?s checks payable in U.S. dollars if the purchase is for at least 50% of the value of the traveler?s checks.
c. With ATM/debit cards at locations approved by USPS Corporate Treasury where the customer?s personal identification number must be entered on a keypad connected to a credit/debit terminal.