5 C.F.R. § 844.103 – Eligibility.

(a) Except as provided in paragraph (c) of this section, an individual must meet the following requirements in order to receive a disability annuity:
1. (1) The individual must have completed at least 18 months of civilian service that is creditable under FERS, as defined in § 842.304 of this chapter;
2. (2) The individual must, while employed in a position subject to FERS, have become disabled because of a medical condition, resulting in a deficiency in performance, conduct, or attendance, or if there is no such deficiency, the disabling medical condition must be incompatible with either useful and efficient service or retention in the position;
3. (3) The disabling medical condition must be expected to continue for at least 1 year from the date the application for disability retirement is filed;
4. (4) Accommodation of the disabling medical condition in the position held must be unreasonable; and
5. (5) The individual must not have declined an offer of reassignment to a vacant position.
(b) The employing agency must consider a disability applicant for reassignment to any vacant position. The agency must certify to the Office of Personnel Management (OPM) either that there is no vacant position or that, although it made no offer of reassignment, it considered the individual for a vacant position. If an agency offers a reassignment and the individual declines the offer, the individual may appeal the agency's determination that the individual is not disabled for the position in question to the Merit Systems Protection Board under 5 U.S.C. 7701.
(c)
1. (1) Paragraphs (a)(2) through (a)(4) of this section do not apply to a military reserve technician who retires under 5 U.S.C. 8456.
2. (2) An individual who separates from employment as a military reserve technician under circumstances set forth in 5 U.S.C. 8456(a)(1) after reaching age 50 and completing 25 years of service is not entitled to a disability annuity under this part, but is entitled to an annuity under § 842.210 of this chapter.
3. (3) A former military reserve technician is not entitled to an annuity under 5 U.S.C. 8456 based on service as a technician if the technician is subsequently appointed to another position in the Federal Government.