37 CFR § 2.101 - Filing an opposition.
(a) An opposition proceeding is commenced by filing in the Office a timely notice of opposition with the required fee.
(b) Any person who believes that he, she or it would be damaged by the registration of a mark on the Principal Register may file an opposition addressed to the Trademark Trial and Appeal Board. The opposition need not be verified, but must be signed by the opposer or the opposer's attorney, as specified in § 11.1 of this chapter, or other authorized representative, as specified in § 11.14(b) of this chapter. Electronic signatures pursuant to § 2.193(c) are required for oppositions filed through ESTTA under paragraph (b)(1) or (2) of this section.
(1) An opposition to an application must be filed by the due date set forth in paragraph (c) of this section through ESTTA.
(2) In the event that ESTTA is unavailable due to technical problems, or when extraordinary circumstances are present, an opposition against an application based on Section 1 or 44 of the Act may be filed in paper form. A paper opposition to an application based on Section 1 or 44 of the Act must be filed by the due date set forth in paragraph (c) of this section and be accompanied by a Petition to the Director under § 2.146, with the fees therefor and the showing required under this paragraph. Timeliness of the paper submission will be determined in accordance with §§ 2.195 through 2.198.
(3) An opposition to an application based on Section 66(a) of the Act must be filed through ESTTA and may not under any circumstances be filed in paper form.
(c) The opposition must be filed within thirty days after publication (§ 2.80) of the application being opposed or within an extension of time (§ 2.102) for filing an opposition. The opposition must be accompanied by the required fee for each party joined as opposer for each class in the application for which registration is opposed (see § 2.6).
(d) An otherwise timely opposition cannot be filed via ESTTA unless the opposition is accompanied by a fee that is sufficient to pay in full for each named party opposer to oppose the registration of a mark in each class specified in the opposition. A paper opposition that is not accompanied by the required fee sufficient to pay in full for each named party opposer for each class in the application for which registration is opposed may not be instituted. If time remains in the opposition period as originally set or as extended by the Board, the potential opposer may resubmit the opposition with the required fee.
(e) The filing date of an opposition is the date of electronic receipt in the Office of the notice of opposition, and required fee. In the rare instances that filing by paper is permitted under these rules, the filing date will be determined in accordance with §§ 2.195 through 2.198.