USPS Certificate of Mailing: Proof You Mailed It (2026 Guide)
Quick Answer: Certificate of Mailing
- It proves: USPS accepted your mailpiece for mailing on a specific date.
- It does not prove: delivery, tracking, signature, or receipt by the addressee.
- Use Form 3817: for fewer than 3 individual pieces at a retail Post Office.
- Use Form 3665: for 3 or more pieces, often called a firm mailing book.
A USPS Certificate of Mailing is useful when the key question is, "Can I prove I mailed this by a certain date?" It is not the same as Certified Mail. Certificate of Mailing gives you a receipt that USPS accepted the mailpiece. Certified Mail adds tracking and a delivery record. If the document has legal, tax, business, or deadline value, choosing the wrong one can leave you with the wrong kind of proof.
In This Guide
What a Certificate of Mailing Proves
Certificate of Mailing proves that USPS accepted the item for mailing. Think of it as a stamped receipt for the act of mailing, not a tracking service. USPS Postal Explorer is clear that certificates of mailing do not provide a record of delivery, and USPS does not keep copies for you.
That makes it a narrow tool: useful for proving a mailing date, weak if you need to prove the recipient actually got the document.
Good proof for
- Mailing date
- USPS acceptance at the counter
- Your own mailing records
- Deadline files where receipt is enough
Not proof of
- Delivery
- Recipient signature
- Tracking history
- That a specific person received it
PS Form 3817 vs PS Form 3665
USPS uses different certificate forms depending on how many pieces you present.
| Form | Use Case | Best For |
|---|---|---|
| PS Form 3817 | Fewer than 3 individual pieces presented at a retail Post Office. | One-off letters, forms, tax documents, or deadline mailings. |
| PS Form 3665 | 3 or more individual pieces; commonly used as a firm mailing book. | Batch business mailings where you need a record for multiple recipients. |
| Certificate of Bulk Mailing | Bulk acceptance record. | Proving a bulk mailing was accepted, not proving a piece went to a specific address. |
If you are dealing with PS Form 3665 specifically, use our PS Form 3665 guide for the form-specific walkthrough.
Certificate of Mailing vs Certified Mail
The simple rule: Certificate of Mailing proves you sent it. Certified Mail helps prove what happened after USPS accepted it.
| Feature | Certificate of Mailing | Certified Mail |
|---|---|---|
| Proof of mailing | Yes | Yes |
| Tracking number | No | Yes |
| Delivery record | No | Yes |
| Optional return receipt | No | Yes |
| Best use | Proving you mailed by a date. | Proving mailing and documenting delivery attempts or delivery. |
If this is legal, business, or high-stakes, Certified Mail is usually safer
Certificate of Mailing can be enough when the only issue is the mailing date. But if the other side may claim they never got it, you usually want Certified Mail, and possibly a return receipt.
When to Use Certificate of Mailing
Use it when the real requirement is "prove I mailed this by a deadline" and you do not need delivery tracking. Common examples:
- Tax or government paperwork: when a mailing date record is useful for your files.
- Insurance paperwork: when you need a simple proof-of-mailing receipt.
- Business correspondence: when you want a low-friction mailing log for non-critical documents.
- Batch notices: when your company sends several notices and needs a mailing record, especially with PS Form 3665.
How to Get a Certificate of Mailing
- Prepare the letter or document. Make sure the recipient address is complete. Use our USPS address lookup guide if you need to verify it first.
- Choose the correct form. Use PS Form 3817 for one or two pieces, or PS Form 3665 for three or more pieces.
- Go to a Post Office retail counter. Present the mail and form before mailing. Do not drop it in a blue box first.
- Pay postage and the certificate fee. USPS calculates the current cost at the counter.
- Keep the stamped receipt. Store it with a copy of what you mailed and any deadline notes.
Need proof after mailing, not just proof you mailed?
The Letter Pilot sends USPS Certified Mail online. Upload your document, enter the address, and we handle printing, postage, tracking, and mailing.
Send Certified Mail OnlineFAQs
What is a USPS Certificate of Mailing?
A USPS Certificate of Mailing is a receipt showing that USPS accepted your mailpiece for mailing on a specific date. It proves mailing, not delivery.
Does Certificate of Mailing include tracking?
No. Certificate of Mailing does not include tracking, delivery confirmation, or a recipient signature. Use Certified Mail if you need tracking or delivery proof.
Which form do I need for Certificate of Mailing?
USPS lists Form 3817 for fewer than three individual pieces presented at a retail Post Office and Form 3665 for three or more pieces.
Is Certificate of Mailing the same as Certified Mail?
No. Certificate of Mailing only proves that you mailed something. Certified Mail provides proof of mailing plus tracking and a delivery record.
Can I get a Certificate of Mailing after I already mailed the letter?
No. You need to present the mail and request the certificate at the time of mailing. USPS does not issue it retroactively after you drop a letter in a mailbox.
Related Guides
- How to Prove You Mailed Something
- PS Form 3665: Certificate of Mailing
- What Is Certified Mail?
- Certified Mail vs Return Receipt
- Certified Mail Forms Guide
- Best USPS Service for Important Documents
Plain-English disclaimer
This guide explains USPS mailing services. It is not legal advice. If a statute, court order, contract, agency rule, or attorney tells you to use a specific mailing method, follow that requirement.
Source: USPS Postal Explorer, Domestic Mail Manual section 503.