37 CFR § 2.35 - Adding, deleting, or substituting bases.
(a) In an application under section 66(a) of the Act, an applicant may not add, substitute or delete a basis, unless the applicant meets the requirements for transformation under section 70(c) of the Act and § 7.31 of this chapter.
(b) In an application under section 1 or section 44 of the Act:
(1) Before publication for opposition, an applicant may add or substitute a basis, if the applicant meets all requirements for the new basis, as stated in § 2.34, § 2.44, or § 2.45. The applicant may delete a basis at any time.
(2) After publication, an applicant may add or substitute a basis in an application that is not the subject of an inter partes proceeding before the Trademark Trial and Appeal Board, but only with the express permission of the Director, after consideration on petition. Republication will be required. The amendment of an application that is the subject of an inter partes proceeding before the Board is governed by § 2.133(a).
(3) When an applicant substitutes one basis for another, the Office will presume that there was a continuing valid basis, unless there is contradictory evidence in the record, and the application will retain the original filing date, including a priority filing date under section 44(d), if appropriate.
(4) If an applicant properly claims a section 44(d) basis in addition to another basis, the applicant will retain the priority filing date under section 44(d) no matter which basis the applicant perfects.
(5) The applicant may add or substitute a section 44(d) basis only within the six-month priority period following the filing date of the foreign application.
(6) When the applicant adds or substitutes a basis, the applicant must list each basis and specify the goods, services, or collective membership organization to which that basis applies.
(7) When the applicant deletes a basis, the applicant must also delete any goods, services, or collective membership organization covered solely by the deleted basis.
(8) Once an applicant claims a section 1(b) basis as to any or all of the goods or services, or a collective membership organization, the applicant may not amend the application to seek registration under section 1(a) of the Act for identical goods or services or the same collective membership organization, unless the applicant files an allegation of use under section 1(c) or section 1(d) of the Act.