A "Certificate Of Service" is used to attest that you (or your attorney or designated agent) has directed documents to another party, typically the opposing counsel and/or other relevant parties involved in litigation.
"Certificates Of Service" are often used by pro se litigants when sending legal documents.
CERTIFICATE OF SERVICE
I HEREBY CERTIFY that on this _______ day of ___________, 2001, a [insert name of document here], was sent via United States Postal Service first class mail, with adequate postage prepaid to [insert name and address of opposing counsel] attorney for the Plaintiff/Defendant: [insert name of person you are litigating against].
______________________ Your Name Defendant/Plaintiff Pro Se
State the full name of the document(s) you are sending, i.e. "Interrogatory Questions for Jane Smith", "Case Pleading", Motion For Hearing", etc. If the document has an identification number on it, include it in the description.
If you intend to send the document by certified mail, FAX, UPS, Federal Express, or another carrier, replace "United States Postal Service" with the name of the alternate carrier. Be aware that FAXing legal documents is not authorized by the rules of procedure in some jurisdictions.
List the name(s) and address(s) of any additional recipients you are sending the document to.