42 C.F.R. § 423.568 Standard timeframe and notice requirements for coverage determinations.
Title 42 - Public Health
(a) Timeframe for requests for drug benefits. When a party makes a request for a drug benefit, the Part D plan sponsor must notify the enrollee (and the prescribing physician involved, as appropriate) of its determination as expeditiously as the enrollee's health condition requires, but no later than 72 hours after receipt of the request, or, for an exceptions request, the physician's supporting statement. (b) Timeframe for requests for payment. When a party makes a request for payment, the Part D plan sponsor must notify the enrollee of its determination no later than 72 hours after receipt of the request. (c) Written notice for denials by a Part D plan sponsor. If a Part D plan sponsor decides to deny a drug benefit, in whole or in part, it must give the enrollee written notice of the determination. (d) Form and content of the denial notice. The notice of any denial under paragraph (c) of this section must— Use approved notice language in a readable and understandable form; State the specific reasons for the denial; Inform the enrollee of his or her right to a redetermination; (i) For drug coverage denials, describe both the standard and expedited redetermination processes, including the enrollee's right to, and conditions for, obtaining an expedited redetermination and the rest of the appeals process; (ii) For payment denials, describe the standard redetermination process and the rest of the appeals process; and Comply with any other notice requirements specified by CMS. (e) Effect of failure to meet the adjudicatory timeframes. If the Part D plan sponsor fails to notify the enrollee of its determination in the appropriate timeframe under paragraphs (a) or (b) of this section, the failure constitutes an adverse coverage determination, and the plan sponsor must forward the enrollee's request to the IRE within 24 hours of the expiration of the adjudication timeframe.
Title 42: Public Health
PART 423—VOLUNTARY MEDICARE PRESCRIPTION DRUG BENEFIT
Subpart M—Grievances, Coverage Determinations, and Appeals
§ 423.568 Standard timeframe and notice requirements for coverage determinations.

