PS Form 6401 at a glance
What it is: PS Form 6401, Money Order Inquiry, is the form to get a copy of a cashed money order or request a refund.
Where and when to file: File the inquiry at any Post Office, and use one form for each money order. File an inquiry about a money order any time after purchase.
A filled-in PS Form 6401 example: an individual customer requests a refund

How to fill out PS Form 6401, box by box
Money Order Serial No., Post Office No., Date and Amount
Purchaser's name, Mailing Address and Telephone No.

Write the Purchaser's First Name (Not for Bank Use), the MI and the Purchaser's Last Name.
Write the Mailing Address (For mailing refund, correspondence, or copies), then Apt. or Suite No., City, State, ZIP+4 and Country (If applicable).
The telephone number fields are optional: include the area code in Telephone No., and fill International Telephone No. if applicable.
Bank Use Only and Bank or Post Office Use Only boxes

Boxes titled Bank Use Only and Bank or Post Office Use Only are not required for individual customers.
The ABA number is required for bank inquiries.
A bank inquiry must include the business/organization name and address.
On an Internal Money Order Inquiry Submitted by U.S. Postal Service, include the USPS organization name on the line titled Bank Use or Post Office Use Only (Bank/Financial Institution Name or Post Office), address and date from the original receipt.
For bank requests, customer photo ID, government issue ID, and customer receipt are not required.
Bank inquiries do not require a fee; this service is provided free of charge.
Certification and Signature

Sign the form in Signature of Customer Filing the Money Order Inquiry and enter the date in the box titled Date Signed (MM-DD-YYYY).
Anyone who furnishes false or misleading information on this form may be subject to criminal sanctions (including fines and imprisonment) and/or civil sanctions (including multiple damages and civil penalties).
By signing, you agree to repay the Postal Service, upon demand, the amount of the refund if the designated payee, purchaser, or financial institution cashes the original money order.
More rules for PS Form 6401
In Section A, use Black Ink ONLY and print within the boxes.
Complete all blocks, sign, and present your customer receipt to the Post Office employee, who will verify the information you provide.
Show your money order customer receipt and personal identification to the sales and service associate at the service window.
After you file an inquiry, you can check the status by calling the toll-free number 1-866-974-2733.
Section B is for official use only.
Common questions about PS Form 6401
What is PS Form 6401?
PS Form 6401, Money Order Inquiry, is the form to get a copy of a cashed money order or request a refund. A refund is issued 60 days or later from the issue date of the money order, or a copy of the money order is provided if it has been cashed.
Where do I file it?
File the inquiry at any Post Office, and use one form for each money order.
Are there fees?
You must pay a separate fee for each form (i.e., money order inquiry).
Sources
[1] PS Form 6401 (August 2016), Money Order Inquiry, U.S. Postal Service (the Official source link on this page).

