MAC and ZPIC reviewers have the right to request additional documentation when a claim itself is insufficient to make a payment determination. Effective April 6, 2015, in response to a pre-payment review and additional documentation request issued by a MAC or ZPIC, providers and suppliers will be limited to a 45 calendar day timeframe to produce the requested documentation and should no longer have any expectation that a request for an extension of time will be granted. This is because CMS has specifically issued instructions to MAC and ZPIC reviewers that they should no longer grant extensions of time, and that they shall deny claims for which the requested documentation was not received by calendar day 46. CMS previously issued Transmittal 567, Change Request 8563, which incorporated these changes into the Medicare Program Integrity Manual, Chapter 3 Verifying Potential Errors and Tracking Corrective Actions, Section 126.96.36.199. Providers and suppliers should ensure that their billing staff and compliance team are aware of these important timing changes.