PS Form 3817, the USPS Certificate of Mailing, is a receipt proving you handed a specific piece of mail to the Postal Service on a specific date. To use it, fill the form out in ink with your name and address, the recipient’s name and address, and (optionally) the postage paid; then bring the form and the mailpiece together to a retail post office counter, where a clerk verifies the match, collects the $2.40 fee, applies the round-date postmark, and hands the postmarked form back to you as your proof. It works for domestic and international mail and for any class of service, but it does not track the item or prove delivery.
Filling Out the Form
Pick up a blank Form 3817 at any post office, or download the PDF from about.usps.com/forms/ps3817.pdf and print it at home. Complete it before you reach the counter. The Domestic Mail Manual requires every entry to be typed, printed in ink or ballpoint pen, or computer-generated. Pencil is not accepted.
The form asks for four things:
- Your name and address, exactly as they appear in the return-address area of the mailpiece.
- The recipient’s full delivery address, matching what is on the envelope or package.
- The postage amount paid on the mailpiece. This field is optional under the DMM, but filling it in ties the certificate to the specific item.
- The fee payment area, where you can affix stamps or a meter strip for the $2.40 certificate fee. The clerk can also collect the fee at the register.
Match the mailpiece exactly. If the envelope says “J. Smith” and the form says “John Smith,” a clerk may flag the mismatch. You can add an invoice number or order reference as an optional notation; the DMM allows it.
Draw a diagonal line through any unused addressee lines. The DMM requires you to obliterate the unused portion of the addressee column so nothing can be added later. If you make a mistake, initial the correction. The acceptance clerk will initial it too.
Submitting It at the Counter
Form 3817 has to be presented in person, with the mailpiece, at a retail post office counter. It cannot be dropped in a blue collection box, left in a lobby slot, or submitted online. A postal employee needs to verify the form against the mailpiece and apply the postmark that makes the certificate official.
At the counter the clerk will:
- Check that the names and addresses on the form match the envelope or package.
- Confirm that proper postage for your mail class is affixed to the mailpiece itself.
- Collect the $2.40 certificate fee, which is separate from postage.
- Apply the round-date postmark to the form, locking in the date and location.
The postmarked form comes back to you as your receipt. The mailpiece goes into the mail stream. Because the certificate is an add-on service rather than a mail class, you can request one for First-Class, Priority Mail, or any other class.
You can present a maximum of two Form 3817 certificates at once. Bring two completed forms, one attached by the stub to each piece. For three or more items, use Form 3665 instead.
What the Certificate Actually Proves
A Certificate of Mailing proves one thing: you gave a specific mailpiece to USPS on the date shown in the postmark. That is useful when a contract, court rule, insurance policy, or agency deadline turns on the date mailed.
It does not prove delivery. There is no tracking number, no delivery scan, no signature, and no insurance. If the mailpiece is lost, the certificate does not help you recover it or file a claim. It only confirms you sent something.
Why It Is Not Enough for the IRS
This is where people get tripped up. A Certificate of Mailing is not the same as certified or registered mail under federal tax law. Under 26 U.S.C. § 7502, only registered mail and certified mail provide prima facie evidence that a tax return was delivered to the IRS. Form 3817 is not named in that statute.
In practice, if a return arrives late or never arrives, a Certificate of Mailing will not save you. The IRS has taken the position that Form 3817 does not conclusively prove the mailing date of a tax return and cannot override a late postmark on the envelope. If the envelope postmark is missing or unreadable, the certificate can support your case, but the IRS may still require more evidence.
For a tax return, an amended return, or a payment mailed close to a deadline, use certified mail with a return receipt. That is the service the statute recognizes.
Outside the IRS context, many courts and agencies do accept a Certificate of Mailing as proof a deadline was met, but the specific rule controls. If it requires “proof of mailing,” Form 3817 works; if it requires “proof of delivery,” it does not. Read the rule before you choose the service.
Keeping the Receipt
USPS does not keep copies of Form 3817. Once the clerk hands it back, the postmarked paper is the only evidence the mailing happened. There is no database, no digital backup, and no way to request a replacement from USPS if you lose it. Store the original somewhere secure, and consider scanning it and keeping a digital copy alongside the physical one. If you need it for a legal or tax matter, treat it like a canceled check.
Duplicate Copies
If you want a second copy, you can request a duplicate at the time of mailing or later. To get one after the original transaction, bring the original postmarked Form 3817 back to a post office along with a new form endorsed “DUPLICATE.” The clerk postmarks the duplicate with the current date. A separate fee applies for each duplicate; the current amount is in USPS Notice 123.
When to Use Form 3665 Instead
Form 3817 covers one or two mailpieces at a time. For three or more pieces at once, use PS Form 3665, the Certificate of Mailing for Firm mailings, which lists multiple recipients on a single sheet. Mailings under 50 pieces and under 50 pounds go to a retail counter; mailings of 50 or more pieces, or 50 pounds or more, go to a Business Mail Entry Unit or an authorized detached mail unit. The clerk postmarks the sheet, which becomes your receipt for the whole batch.
Certificate of Mailing vs. Certified Mail
The names sound alike, but the two services do different jobs at different prices.
- Certificate of Mailing (Form 3817) proves you mailed something on a certain date. No tracking, no delivery confirmation, no signature. $2.40.
- Certified Mail provides a tracking number, an electronic delivery record, and optionally a signed return receipt showing who accepted the item. It qualifies as prima facie evidence of delivery under 26 U.S.C. § 7502 for IRS filings. It costs significantly more.
Use the Certificate of Mailing when you only need to document the date you sent something and the consequences of non-delivery are limited. Use certified mail when you need to prove the recipient received it, or when a statute or rule specifically requires certified or registered service. For anything involving the IRS, certified mail is the safer choice.