According to the United States Postal Service, while the exact location of a postal money order cannot be traced, customers can determine whether a specific money order has been cashed by contacting the USPS with information contained on the money order's receipt. The customer must fill out Form 6401, usually at a post office, and pay a fee to make a tracing inquiry.
Customers allowed to trace the payment of a postal money order include the purchaser of the money order, the payee or any endorser listed on the order. Parents of minor children and those who legally and financially represent the payee may also trace the postal order.
The USPS does not charge customers a fee if the trace is done by a bank or financial institution on the customers' behalf, according to their site. Only one money order can be traced per form and fee. Form 6401 must still be filled out by the inquiring institution to perform the trace.
Other entities capable of performing a search include postal officials, as long as the trace is officially USPS business, and government agencies involved with processing postal money orders with the Federal Reserve. The postmaster general also has the authority to refuse the payment of money orders.