Section 425.659 - Calculating risk scores used in Shared Savings Program benchmark calculations(a)General. CMS accounts for differences in severity and case mix of the ACO's assigned beneficiaries and assignable beneficiaries (as defined under § 425.20 ) in calculations used in establishing, adjusting, and updating the ACO's historical benchmark.(b)Prospective Hierarchical Condition Category (HCC) risk score calculation. In determining Medicare FFS beneficiary prospective HCC risk scores for a performance year and each benchmark year of the ACO's agreement period, CMS does the following: (1) CMS specifies the CMS-HCC risk adjustment methodology used to calculate prospective HCC risk scores for Medicare FFS beneficiaries (as defined under § 425.20 ) for use in Shared Savings Program calculations as follows: (i) In calculating risk scores for Medicare FFS beneficiaries for a performance year, CMS applies the CMS-HCC risk adjustment methodology applicable for the corresponding calendar year.(ii) For agreement periods beginning before January 1, 2024, CMS applies the CMS-HCC risk adjustment methodology for the calendar year corresponding to the benchmark year in calculating risk scores for Medicare FFS beneficiaries for each benchmark year of the agreement period.(iii) For agreement periods beginning on January 1, 2024, and in subsequent years, CMS applies the CMS-HCC risk adjustment methodology for the calendar year corresponding to the performance year, as specified under paragraph (b)(1)(i) of this section, in calculating risk scores for Medicare FFS beneficiaries for each benchmark year of the agreement period.(2) CMS does the following to calculate the prospective HCC risk scores identified in paragraph (b)(1) of this section for a benchmark or performance year: (i) Removes the Medicare Advantage coding intensity adjustment, if applicable.(ii) Renormalizes prospective HCC risk scores by Medicare enrollment type (ESRD, disabled, aged/dual eligible Medicare and Medicaid beneficiaries, and aged/non-dual eligible Medicare and Medicaid beneficiaries) based on the national assignable FFS population for the relevant benchmark or performance year.(iii) Calculates the average prospective HCC risk score by Medicare enrollment type (ESRD, disabled, aged/dual eligible Medicare and Medicaid beneficiaries, and aged/non-dual eligible Medicare and Medicaid beneficiaries). 88 FR 79551 , Nov. 16, 2023