37 CFR § 3.41 - Recording fees.
(a) All requests to record documents must be accompanied by the appropriate fee. Except as provided in paragraph (b) of this section, a fee is required for each application, patent and registration against which the document is recorded as identified in the cover sheet. The recording fee is set in § 1.21(h) of this chapter for patents and in § 2.6(b)(6) of this chapter for trademarks.
(b) No fee is required for each patent application and patent against which a document required by Executive Order 9424 is to be filed if:
(1) The document does not affect title and is so identified in the cover sheet (see § 3.31(c)(2)); and
(2) The document and cover sheet are either: Faxed or electronically submitted as prescribed by the Director, or mailed to the Office in compliance with § 3.27.