How to fill out Certified Mail Form 3800 and address the envelope
PS Form 3800 is the USPS Certified Mail receipt: a sticker with a barcode and article number that goes on the envelope, attached to a receipt you keep. Write the recipient’s name and address on the receipt, tick any extra service you are buying, peel off the sticker and place it above the recipient’s address, to the right of the return address. Add postage, have the clerk postmark the receipt, and keep it. The forms are free at any Post Office; certified labels can also be printed through USPS-approved postage software, or skipped entirely by having a service mail it.
Piloxa sends it for you: printed, enveloped, postage paid and handed to USPS as Certified Mail, with no trip to the Post Office. Your first letter is $9.95 all in: one or two pages by Certified Mail with USPS tracking, with printing, the envelope, postage and the certified fee included. You see the exact pages, the recipient and one total before you pay. No subscription.
In short
For someone who does not want to fill in Form 3800, print a label or stand in line, Piloxa prints the letter, applies the certified label, pays the postage and hands it to USPS.
Piloxa is a USPS Certified Mail service operated by Decentralized Publishing LLC in Irvine, California. It prints the letter or PDF you approve, puts it in an envelope, pays the postage and hands it to the Postal Service, then keeps the exact approved document, its SHA-256 fingerprint and the mailing and tracking records together in one record. Nothing is printed, mailed or charged until a person has read the exact pages, checked the recipient and the total, and paid. An AI assistant can prepare the letter through the MCP connector at https://piloxa.com/mcp or the HTTP API described at https://piloxa.com/openapi.json; either way it only gets back a review link for the person to open.
Filling in Form 3800, step by step
- Pick up the form. Form 3800 is free at the Post Office counter and the lobby, usually beside the green return-receipt cards (PS Form 3811).
- Write the recipient on the receipt part. Name, street and apartment or suite, city, state and ZIP Code, the same as on the envelope. This is your copy, so make it legible.
- Tick the extra services you are buying. The receipt has spaces for the return receipt (paper or electronic) and the other extra services. Leave the fee lines for the clerk if you are at the counter, or fill them in from the current price list if you are not.
- Peel off the sticker and put it on the envelope. It goes above the recipient’s address, to the right of the return address. Do not cover the address or the stamp area, and do not fold it over an edge.
- Note the article number. The long number under the barcode is your tracking number. Write it on your own copy of the letter.
- Pay the postage and the fees. At the counter the clerk weighs it and charges postage, the Certified Mail fee and any return receipt together.
- Get the receipt postmarked. The postmarked receipt is your dated proof of mailing. Keep it with your copy of the letter.
Adding a return receipt
Electronic return receipt: tick it on Form 3800 and give the clerk your email address. USPS emails the delivery record, including the signature, after delivery. It costs less than the card.
Green card (PS Form 3811): fill in the recipient’s address in the “article addressed to” area, write your own name and address on the other side, where the card comes back to, and copy the article number from your 3800 sticker onto it. Attach it to the back of the envelope with its adhesive strips. The card is signed at delivery and mailed back to you. Use it when a statute or contract names the card; otherwise the electronic receipt does the same job. See electronic return receipt vs green card.
How to address Certified Mail
| Line | What to write |
|---|---|
| Recipient name | The person’s full name or the company’s legal name, as it appears on the contract, lease or account, not a nickname or brand |
| Attention line (optional) | “Attn: Legal Department” or a named person, on the line under the company |
| Street | Number and street, then the suite, unit or apartment on the same line where it fits |
| City, state, ZIP | The two-letter state abbreviation and the ZIP+4 if you know it |
| Return address | Your name and address in the top left corner; this is where a refused or unclaimed letter comes back |
Use the address the contract or lease names for notices, if there is one; it is often not the office you deal with. A P.O. Box works too; the box holder signs (Certified Mail to a P.O. Box). Keep the space below the address clear, and run any address you are unsure of through the recipient address check.
Certified Mail labels online
If you search for “print certified mail label”, what you find is postage software. USPS-approved PC Postage providers sell electronic Certified Mail labels: you type the address, pay the postage and fees, and print a label with the barcode and postage on it. You still print the letter, stuff and seal the envelope, and drop it off or schedule a pickup, and many of these services charge a monthly subscription. Without a counter, the first USPS scan, often at pickup or at the plant, becomes your mailing date.
Or skip the form entirely
With Piloxa there is no Form 3800 to fill in and no label to print. Paste the letter or attach a PDF, enter the recipient, and see the exact pages and one total. Piloxa prints the letter, applies the certified label, envelopes it, pays the postage and hands it to USPS, then keeps the article number, the printed address and every scan in your record. Your first letter is $9.95 all in. Piloxa sends the electronic return receipt, not the green card.
Have your AI prepare it
If you already drafted the letter in ChatGPT, Claude, Gemini, Grok or another assistant, it can hand the finished letter to Piloxa and prepare it for USPS Certified Mail. Ask it in plain words, for example: I don’t want to fill out Form 3800 or print a label. Prepare this letter for Certified Mail with Piloxa.
The connector address is https://piloxa.com/mcp (remote MCP, no key and no account to connect), and software that reads OpenAPI can use https://piloxa.com/openapi.json. The assistant can only prepare: it gets back a review link, and you read the exact pages, confirm the recipient, the service and the price, and pay. Nothing is printed, mailed or charged before that. What an assistant can and cannot do with Piloxa.
Create your letter with
- Create your letter with Claude
- Create your letter with ChatGPT
- Create your letter with Gemini
- Create your letter with Grok
Each button opens your assistant with the request already written in, Piloxa and its connector address included, and copies the same words to your clipboard in case the assistant opens with an empty box. Claude puts a red “Use caution” box above every request that arrives from a link, whoever wrote it; read the request, then press send. Nothing is printed or mailed until you read the review page and pay. How to connect your assistant
Questions people ask
Can I get Certified Mail Form 3800 online?
The paper form comes from the Post Office, free. Online, the equivalent is an electronic Certified Mail label sold by USPS-approved postage software, or a service that prints and mails the letter for you so there is no form at all.
Where does the Certified Mail sticker go?
Above the recipient’s address, to the right of the return address, without covering either address or the postage.
Do I need a green card as well as Form 3800?
Only if you want the paper return receipt. Form 3800 gives you the mailing receipt and tracking. For a signature record, choose the electronic return receipt on the 3800 or attach PS Form 3811.
Can I drop a certified letter in a mailbox?
Yes, with correct postage and fees, but you lose the postmarked counter receipt, and the mailing date becomes the first USPS scan.
Do I write “Certified Mail” on the envelope?
The sticker already marks it as Certified Mail. Writing the words yourself adds nothing; buying the service is what counts.
Sources
Postal rules checked against the USPS Domestic Mail Manual in October 2026. Legal rules differ by state and by situation.
Related Certified Mail guides
Ready to send it?
Paste the letter or attach the finished PDF. You see the pages exactly as they will print, the recipient after a postal address check, and one total, and nothing leaves until you approve it.