20 CFR § 416.325 - When an application is considered filed.
(a) General rule. We consider an application for SSI benefits filed on the day it is received by an employee at any social security office, by someone at another Federal or State office designated to receive applications for us, or by a person we have authorized to receive applications for us.
(b) Exceptions.
(1) When we receive an application that is mailed, we will use the date shown by the United States postmark as the filing date if using the date the application is received will result in a loss of benefits. If the postmark is unreadable or there is no postmark, we will use the date the application is signed (if dated) or 5 days before the day we receive the signed application, whichever date is later.
(2) We consider an application to be filed on the date of the filing of a written statement or the making of an oral inquiry under the conditions in §§ 416.340, 416.345 and 416.350.
(3) We will establish a “deemed” filing date of an application in a case of misinformation under the conditions described in § 416.351. The filing date of the application will be a date determined under § 416.351(b).