CMS Pub. 100-18, ch. 6, § 30.4.4

Within the first 90 days of coverage under a new plan, plans must provide a transition supply

when the beneficiary requests a non-formulary drug. This 90 day timeframe applies to retail,

home infusion, long-term care, and mail-order pharmacies. CMS believes it makes sense to both

limit and define the amount of time during which a transition process is applicable. Thus, plans

are required to provide a temporary fill anytime during the first 90 days of a beneficiary’s

enrollment in a plan. However, since certain enrollees may join a plan at any time during the

year, this requirement applies beginning on such an enrollee’s first effective date of coverage

instead of to the first 90 days of the plan year. If an enrollee leaves a plan and re-enrolls during

the original 90 day transition period, the transition period begins again with the new effective

date of enrollment, because it is possible that the enrollee’s drug therapy changed while the

enrollee was not with the plan and that therapy could be potentially interrupted. However, if

there is no gap in coverage, there is no new transition period.