US · guidance
CMS Pub. 100-05, ch. 5, § 40.8.6.1
Prorating Primary Payments
The A/B MAC (Part A) prorates the undesignated primary payer's payment for
Medicare covered services by applying a ratio of this payment between lab and non-lab
charges on the bill to determine what portion of the primary payer's payment is
attributable to the non-lab charges. Note, the ratio and payment can be done by sending
the claim to the MSPPAY module for payment calculation.
NOTE: This ratio is based upon Medicare billed charges and not Medicare's payment
under the fee schedule.
History
(Rev. 11550; Issued: 08-12-22; Effective: 10-13-22; Implementation:10-13-22)
Provenance
- Source
- cms.gov
- Retrieved
- 2026-08-25
- Edition
- iom-2026-08-25
- Content hash
4072608f7e483e2333b1966d993492825917aec43d9de239b05ebf6682be5dcc
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