20 CFR §220.21

1. (a)In some cases, the Board may determine that a claimant is not currently disabled for work in his or her regular occupation but was previously disabled for a specified period of time in the past. This can occur when—
   1. (1)The disability application was filed before the claimant's occupational disability ended, but the Board did not make the initial determination of occupational disability until after the claimant's disability ended; or
   2. (2)The disability application was filed after the claimant's occupational disability ended but no later than the 12th month after the month the disability ended.
2. (b)When evaluating a claim for a previous occupational disability, the Board follows the steps in § 220.13 to determine whether an occupational disability existed, and follows the steps in §§ 220.16 and 220.17 to determine when the occupational disability ended.