20 C.F.R. § 404.322 When you may apply for a period of disability after a delay due to a physical or mental condition.
Title 20 - Employees' Benefits
If because of a physical or mental condition you did not apply for a period of disability within 12 months after your period of disability ended, you may apply not more than 36 months after the month in which your disability ended. Your failure to apply within the 12-month time period will be considered due to a physical or mental condition if during this time— (a) Your physical condition limited your activities to such an extent that you could not complete and sign an application; or (b) You were mentally incompetent.
Title 20: Employees' Benefits
PART 404—FEDERAL OLD-AGE, SURVIVORS AND DISABILITY INSURANCE (1950– )
Subpart D—Old-Age, Disability, Dependents' and Survivors' Insurance Benefits; Period of Disability
Old-Age and Disability Benefits
§ 404.322 When you may apply for a period of disability after a delay due to a physical or mental condition.