Certified mail
How do I prove I sent a letter before a deadline?
Updated · By the SendMyLettersOnline team
Get dated proof from USPS when you mail it: a Certified Mail receipt (postmarked or with a USPS acceptance scan) or a Certificate of Mailing (PS Form 3817) shows the date the letter entered the mail. Whether mailing on time is enough depends on the rule: federal tax law treats a timely mailed document as timely filed (26 U.S.C. 7502), while many contract and court deadlines count the day it is received.
| Proof | Shows date mailed | Shows delivery | Shows contents |
|---|---|---|---|
| Certificate of Mailing (PS Form 3817) | Yes | No | No |
| Certified Mail receipt + tracking | Yes | Yes (tracking) | No |
| Certified Mail + return receipt | Yes | Yes, with signature | No |
| Our proof-of-mailing PDF | Yes (handoff date) | No | Yes, the exact letter we printed |
| Copy of the letter you keep | No | No | Yes |
Mailing date vs receipt date
- Federal tax returns and payments: the timely-mailing rule in 26 U.S.C. 7502 generally treats the postmark date as the filing date, and a registered or certified mail receipt is evidence of delivery.
- Federal court service of papers by mail: FRCP 5(b)(2)(C) says service by mail is complete on mailing. Filing with the court is a different rule; check the court's.
- Leases, contracts and state notices: read the clause. Many say notice is effective when received or a set number of days after mailing.
Build a paper trail
- Keep the exact letter (PDF) you sent.
- Mail it by Certified Mail; add a return receipt if receipt matters.
- Save the tracking history and the return receipt PDF with the letter.
- If the deadline is today, mail at a post office counter so the receipt is postmarked today.
Quick answers
Does the postmark date count for a legal deadline?
For federal tax filings, generally yes under 26 U.S.C. 7502. For other deadlines it depends on the statute, court rule or contract.
What if my certified mail doesn't arrive before the deadline?
If the rule counts mailing, your receipt shows you mailed in time. If it counts receipt, a late arrival may be a problem; contact the recipient or court quickly with your proof.
How do I prove I mailed a document to the court?
Keep the Certified Mail receipt and tracking, and file a certificate of service if the court rules require one. See prove you mailed a document to court.
What to do next
Send your notice by Certified Mail with return receipt and keep the receipt, tracking and our proof-of-mailing PDF together.
Send with proofSources
- 26 U.S.C. 7502 (timely mailing treated as timely filing)
- Federal Rules of Civil Procedure, Rule 5
- USPS: Insurance & Extra Services (Certificate of Mailing, Certified Mail)
- USPS Domestic Mail Manual 503: Extra Services
Checked: . General information, not legal advice. Fees and rules change: confirm current values at the official links above.