37 CFR § 1.115 - Preliminary amendments.
(a) A preliminary amendment is an amendment that is received in the Office (§ 1.6) on or before the mail date of the first Office action under § 1.104. The patent application publication may include preliminary amendments (§ 1.215(a)).
(1) A preliminary amendment that is present on the filing date of an application is part of the original disclosure of the application.
(2) A preliminary amendment filed after the filing date of the application is not part of the original disclosure of the application.
(b) A preliminary amendment in compliance with § 1.121 will be entered unless disapproved by the Director.
(1) A preliminary amendment seeking cancellation of all the claims without presenting any new or substitute claims will be disapproved.
(2) A preliminary amendment may be disapproved if the preliminary amendment unduly interferes with the preparation of a first Office action in an application. Factors that will be considered in disapproving a preliminary amendment include:
(i) The state of preparation of a first Office action as of the date of receipt (§ 1.6) of the preliminary amendment by the Office; and
(ii) The nature of any changes to the specification or claims that would result from entry of the preliminary amendment.
(3) A preliminary amendment will not be disapproved under (b)(2) of this section if it is filed no later than:
(i) Three months from the filing date of an application under § 1.53(b);
(ii) The filing date of a continued prosecution application under § 1.53(d); or
(4) The time periods specified in paragraph (b)(3) of this section are not extendable.