2220 Certificate of Service [R-07.2015]
If the requester of a request filed under 35 U.S.C. 302 is a person other than the patent owner, the owner of the patent must be served with a copy of the request in its entirety. The service must be made on the patent owner’s correspondence address as indicated in 37 CFR 1.33(c). The third party requester must set forth on the certificate of service the name and address of the party served and the method of service. The certificate of service must be attached to the request submitted to the Office. Further, the copy of the request served on the patent owner must also include a copy of the certificate of service. If service was not possible after a reasonable effort to do so, a duplicate copy of the request papers must be supplied to the Office together with a cover letter including an explanation of what effort was made to effect service, and why that effort was not successful. To avoid the possibility of the Office erroneously charging a duplicate filing fee, requesters are strongly encouraged to clearly word the cover letter by stating, for example, in bold print in the heading "Duplicate Copy of Request Filed under 37 CFR 1.510(b)(5) When Service on the Patent Owner Was Not Possible."
See MPEP § 2266.03 regarding service on the requester and on the patent owner.