37 CFR § 1.54 - Parts of application to be filed together; filing receipt.
(a) It is desirable that all parts of the complete application be deposited in the Office together; otherwise, a letter must accompany each part, accurately and clearly connecting it with the other parts of the application. See § 1.53 (f) and (g) with regard to completion of an application.
(b) Applicant will be informed of the application number and filing date by a filing receipt, unless the application is an application filed under § 1.53(d). A letter limited to a request for a filing receipt may be signed by a juristic applicant or patent owner.