(a) Every paper filed in the United States Patent and Trademark Office in inter partes cases, including notices of appeal, must be served upon the other parties. Proof of such service must be made before the paper will be considered by the Office. A statement signed by the attorney or other authorized representative, attached to or appearing on the original paper when filed, clearly stating the date and manner in which service was made will be accepted as prima facie proof of service.
(b) Service of papers must be on the attorney or other authorized representative of the party if there be such or on the party if there is no attorney or other authorized representative, and may be made in any of the following ways:
(1) By delivering a copy of the paper to the person served;
(2) By leaving a copy at the usual place of business of the person served, with someone in the person's employment;
(3) When the person served has no usual place of business, by leaving a copy at the person's residence, with a member of the person's family over 14 years of age and of discretion;
(4) Transmission by the “Express Mail Post Office to Addressee” service of the United States Postal Service or by first-class mail, which may also be certified or registered;
(5) Transmission by overnight courier.
Whenever it shall be satisfactorily shown to the Director that none of the above modes of obtaining service or serving the paper is practicable, service may be by notice published in the Official Gazette.
(6) Electronic transmission when mutually agreed upon by the parties.
(c) When service is made by first-class mail, “Express Mail,” or overnight courier, the date of mailing or of delivery to the overnight courier will be considered the date of service. Whenever a party is required to take some action within a prescribed period after the service of a paper upon the party by another party and the paper is served by first-class mail, “Express Mail,” or overnight courier, 5 days shall be added to the prescribed period.
(d) If a party to an inter partes proceeding is not domiciled in the United States and is not represented by an attorney or other authorized representative located in the United States, the party may designate by document filed in the United States Patent and Trademark Office the name and address of a person residing in the United States on whom may be served notices or process in the proceeding. If the party has appointed a domestic representative, official communications of the United States Patent and Trademark Office will be addressed to the domestic representative unless the proceeding is being prosecuted by an attorney at law or other qualified person duly authorized under § 11.14(c) of this subchapter. If the party has not appointed a domestic representative and the proceeding is not being prosecuted by an attorney at law or other qualified person, the Office will send correspondence directly to the party, unless the party designates in writing another address to which correspondence is to be sent. The mere designation of a domestic representative does not authorize the person designated to prosecute the proceeding unless qualified under § 11.14(a), or qualified under § 11.14(b) and authorized under § 2.17(f).
(e) Every paper filed in an inter partes proceeding, and every request for an extension of time to file an opposition, must be signed by the party filing it, or by the party's attorney or other authorized representative, but an unsigned paper will not be refused consideration if a signed copy is submitted to the Patent and Trademark Office within the time limit set in the notification of this defect by the Office.