How to File a USPS Money Order Inquiry With PS Form 6401

PS Form 6401 is the USPS money order inquiry form you file when a money order has been lost, stolen, or cashed by the wrong person, and it currently costs $21.00 per inquiry. You submit it in person at any post office with your original purchase receipt, and USPS then either sends you a copy of the cashed money order or, if it was never cashed, issues a replacement.

Before you pay the fee, run the free status check. USPS lets you look up whether a money order has already been cashed at tools.usps.com/money-orders.htm using three items from your receipt: the serial number, the post office number, and the exact dollar amount.¹ If the tool shows the money order was cashed and that matches what your recipient told you, you have your answer without filing anything. If it shows uncashed and the recipient says it never arrived, that is when Form 6401 becomes necessary.

When PS Form 6401 Is the Right Tool

The inquiry exists for situations a status check cannot resolve. The most common one: you mailed a payment, the recipient insists it never arrived, and you need to know whether it was cashed by someone else or is still floating in the mail. Filing produces either a copy of the endorsed money order or confirmation that it remains uncashed, which then triggers a replacement.²

You would also use Form 6401 if you suspect fraud. The copy USPS sends back shows the endorsement on the back, so you learn who signed for the money. That image is often the first piece of evidence in a fraud report or civil claim.

One thing to be clear about: USPS does not offer stop payments on money orders.³ You cannot call and cancel one the way you would a personal check. The inquiry is the only recourse. The same form and procedure apply whether the money order was domestic or international.⁴

What to Have Ready

Everything runs on the original purchase receipt. Pull it out before you head to the post office and confirm it has:

The serial number, which is the primary way USPS locates the money order in its system.
The post office number. The form asks for the 10-digit finance number of the issuing office (a 6-digit finance number plus a 4-digit unit ID), or the ZIP code where you bought it.²
The exact dollar amount. It has to match to the cent. A money order purchased for $347.50 will not surface if you write $347.
The date of purchase.
Your name and mailing address, since USPS sends the results and any replacement there.

Every money order needs its own form and its own $21.00 fee. Three missing money orders means three inquiries.²

If You Lost the Receipt

You can still submit Form 6401 without the receipt, but you have to supply the same required information, including the serial number and post office number.⁴ That is the catch. USPS clerks cannot search by your name or the date of purchase, so if you have no way to recover the serial number, the inquiry has nothing to run against. Check the detachable stub from the money order itself if you kept it, along with any phone photos or bank records that might show the number. Otherwise the inquiry cannot move forward.

Filing at the Post Office

Bring the receipt to any post office and tell the clerk you need to file a money order inquiry. The clerk provides PS Form 6401, checks that your information is complete, and submits it.² You cannot file it yourself online or by mail; it has to go through a clerk. You pay the $21.00 fee at the counter. Keep the receipt they give you as proof you filed. You can track the inquiry afterward through the same online tool you used to check status.³

There is no mandatory waiting period before you can file. If you mailed a money order yesterday and already know something went wrong, you can walk in today.⁴

What You Get Back, and When

Your form goes to the USPS Money Order Branch, which searches accounting records for a digital image of the processed money order. Two outcomes are possible.

If It Was Cashed

USPS mails you a copy of the cashed money order showing the endorsement. Confirming loss or theft this way can take up to 30 days.³ If the signature is not your intended recipient’s, you now have documentation of an improper payment, which is what a fraud claim or lawsuit will need.

If It Was Not Cashed

USPS issues a replacement money order for the original amount. The replacement is not issued until at least 60 days after the original purchase date, and the full investigation itself can also run up to 60 days.⁴³ The 60 days runs from when you bought the money order, not from when you filed the inquiry, so filing early does not shorten the wait for a replacement, only the wait for information.

Damaged Money Orders Are a Different Process

If the money order is physically damaged or printed incorrectly and you still have it, do not file Form 6401. Bring the damaged money order and your receipt to any post office and USPS will replace it at no charge.³ The $21.00 fee only applies to lost or stolen money orders that need an investigation.

The One-Year Deadline for Improper Payment

If someone cashed your money order who should not have, you have one year from the date it was paid to file a claim. After that, USPS will not act on it, even with proof.⁴ Postal money orders themselves never expire, so an uncashed one that sat in a drawer for years is still good, but the window to challenge a bad payment is finite. If you have any suspicion the money order was cashed by the wrong person, file the inquiry well inside that year.

1
USPS.com. Money Orders
2
United States Postal Service. PS Form 6401 – Money Order Inquiry
3
United States Postal Service. Sending Money Orders
4
United States Postal Service. Money Orders – The Basics