ANSWER: Yes. You cannot apply for disability retirement after being separated from government service for one year. To meet the time deadline, your application must be filed with OPM within one year of the date you leave your government job. There is an exception, under special circumstances, for persons who are mentally incapacitated.
Employees separated for more than 31 days may file an application for disability retirement with their agency, but are best advised to file directly with OPM. Employees who are near the expiration of the one year time limit should file directly with OPM to preclude the possibility of the agency's delaying the application from reaching OPM until after the time limit.