New CMS Medicaid Rate Guide Takes Effect July 1: What MLTSS and ILOS Documentation Shifts Mean for Actuaries Certifying Now

The CMS 2026-2027 Medicaid Managed Care Rate Development Guide, published February 19, 2026, applies to all rating periods beginning between July 1, 2026 and June 30, 2027. For actuaries certifying Medicaid managed care rates right now, it requires separate service category documentation for MLTSS programs and a new standalone ILOS cost certification, converting previously discretionary data-gathering into formal actuarial opinion deliverables with their own ASOP No. 49 professional standards exposure (CMS, February 2026).

The Enrollment Data Environment Underneath the Guide

National Medicaid enrollment peaked at roughly 94 million in early 2023 when the continuous enrollment provision ended, then fell to approximately 67 million by mid-2026 after more than two years of post-COVID redeterminations, with roughly 27 million people disenrolled during the unwinding period and state-level disenrollment rates ranging from 12% in North Carolina to 57% in Montana (KFF, 2026; GAO, 2025). That 27-million swing represents the largest structural population shift in program history, and it has not finished running.

The claims data that forms 2026 base periods reflects an in-between population. Not the pre-COVID enrolled mix, which included millions of people retained under continuous enrollment who would otherwise have cycled off through redeterminations. Not the post-OBBBA equilibrium, which does not yet exist. Actuaries selecting experience data for July 2026 certifications are working with a two-to-three-year claims record from a period that was itself transitional, compounded by OBBBA work requirements and the six-month redetermination cycle beginning in late 2026.

The 2026-2027 guide's release in February 2026 means the standard actuaries were trained on, the 2025-2026 guide, governed certifications for periods beginning July 2025. The documentation bar has risen at every annual renewal for three consecutive years, with each successive guide layering new requirements on a certification process designed for a relatively stable enrolled population with several continuous years of claims experience. The cumulative effect is that the 2026-2027 guide arrives precisely when the underlying data it is meant to document is least reliable.

P&C actuaries working tariff severity triangles after significant market disruptions recognize the structural analogue: the base period reflects a risk pool that no longer exists, and the current pool lacks enough loss history to substitute. The solution in both contexts is explicit population composition adjustments with disclosed uncertainty ranges, not reliance on historical trend factors that assume a stable underlying mix. Medicaid managed care actuaries in 2026 are making the same methodological choice under the same data conditions, with a new guide that raises the documentation standard for every component of the certification.

MLTSS Programs: Separate Service Category Documentation

Twenty-five states operate MLTSS programs as of 2025, up from 12 states in 2011 (CMS, 2025). These programs deliver long-term services and supports through capitated managed care, covering populations that include elderly adults, individuals with physical disabilities, and people with developmental disabilities. Prior rate development guides allowed states to present blended MLTSS rate cells that aggregated costs across service types within a program segment. The 2026-2027 guide requires actuaries to separately document and justify each distinct service category.

The four categories that states must now document separately are: personal care services, home health services, residential services including assisted living and adult family care homes, and facility-based services including nursing facility care. Each carries distinct cost drivers and trend dynamics. Personal care is predominantly a labor cost, sensitive to minimum wage changes and home care workforce turnover in tight labor markets. Home health involves both clinical staffing and aide services, with utilization often driven by post-acute discharge patterns that run on a different trend than long-term custodial care. Residential placements are shaped by bed availability and the state's HCBS waiver capacity. Facility-based nursing care is driven by clinical acuity, length-of-stay trends, and state staffing mandates that have shifted materially since 2020.

Presenting these as a single blended rate cell masks the actuarial assumptions embedded in each component and makes post-certification attribution of rate inadequacy nearly impossible. When a blended MLTSS rate proves insufficient in hindsight, it is difficult to identify whether the miss came from personal care utilization growth, residential placement rates, or a nursing facility cost spike. The new guide's requirement to separately document each category creates at least four additional actuarial opinion sections per MLTSS population segment, plus a reconciliation to the blended rate that the MCO contract ultimately uses.

What the separate documentation requirement means in practice is that each category section must include a data summary identifying the source, years of experience, method of disaggregation from blended plan encounter data, and credibility weight; a trend analysis with separate trend factors for that service type and an explanation of the forces driving category-specific trends; a credibility assessment indicating whether category-level experience meets the ASOP No. 49 credibility threshold or requires blending with data from comparable programs; and a rate cell derivation showing how the category component feeds into the blended MLTSS total.

The data availability gap is immediate. Many MLTSS states collect utilization and cost data at the plan level because managed care claims adjudication does not always require service category disaggregation at the source. States that have relied on aggregate encounter reports from their managed care plans need to work with those plans to produce claims-level data cuts disaggregated by service type. The data request, quality review, categorization judgment calls for borderline service codes, and actuarial assessment of the resulting data all add time to a certification process that was already running against a July 1 deadline. States that collect MLTSS data at the service authorization level, where authorization codes typically identify service type, are in a better position to produce this documentation quickly.

The professional standards implication follows directly. ASOP No. 49 Section 3.2 requires the actuary to use data that is "relevant and sufficient." Category-level data gaps that could previously be absorbed into a blended rate are now each a potential Section 3.5 disclosure item: what data was used, why it was the best available, and what the uncertainty range looks like at the service category level.

ILOS Certification in Appendix B: Formal Opinion on Thin Data

In lieu of services are alternatives that managed care plans offer as medically appropriate, cost-effective substitutes for covered state plan services. CMS accumulated ILOS reporting across multiple cycles and found wide variation in how states and plans documented cost offsets from these substitutions. The 2026-2027 guide's Appendix B is the direct response: a mandatory standalone deliverable that converts ILOS cost documentation from a discretionary section of the actuarial report into a required package with a defined structure and an explicit CMS review trigger.

Every rate certification must now include an Appendix B ILOS documentation package containing a summary of actual managed care plan ILOS costs based on plan-reported claims and encounter data, the ILOS Cost Percentage calculated as total ILOS expenditures (excluding short-term IMD stays) divided by total actual capitation payments for the rating period, and a certification from the state's actuary confirming the data is accurate to the best of their knowledge and consistent with applicable CMS guidance (CMS 2026-2027 Rate Guide, February 2026; 42 CFR 438.4).

The ILOS documentation requirement stands as the most operationally significant update in the 2026-2027 guide because it converts a data-gathering question into a formal actuarial opinion deliverable with its own professional standards exposure. Prior guides acknowledged ILOS costs as a component of the rate certification but left the documentation standard largely to state and actuary discretion. Appendix B formalizes that discretion into a required deliverable with specific data elements, an actuary-signed certification, and a CMS review process that now treats documentation deficiencies as grounds for a formal comment letter rather than a request for clarification.

For newly approved ILOS items, this is where the professional standards tension is sharpest. When a state launches a new ILOS, a hospital-at-home program, a specialized housing placement, or an expanded respite service, the first certification cycle occurs with zero state-specific utilization and cost data for that item. The actuary must render an opinion on a cost component built from analog data drawn from similar programs elsewhere, plan projections, and clinical assumptions rather than the state's own experience. Whether that basis meets ASOP No. 49's credibility standard is a judgment call, but the standard sets a bar that first-cycle ILOS data is unlikely to clear without explicit qualification.

Three professional paths are available. The actuary can certify using the best available data with a Section 3.5 disclosure that names the credibility limitation, describes the analog data or methodology used in its place, and quantifies the uncertainty range to the extent practicable. The actuary can issue a qualified opinion that explicitly constrains what the certification covers with respect to the ILOS component. Or the actuary can decline to certify the ILOS cost element at all, requiring the state to carry that service in fee-for-service until credible state-specific data accumulates. Each path carries different implications for the MCO's financial planning, the state's rate amendment timeline, and the enrollees whose care depends on the ILOS appearing in the managed care benefit rather than the carve-out.

The CMS Comment Letter Mechanism and Project Timeline Risk

The March 11, 2026 Managed Care Monitoring and Oversight CIB from CMS made the review consequence explicit: rates for ILOS not supported by state-specific utilization data will generate formal comment letters requiring data collection plans before rates can be approved (CMS CIB, March 2026). This is a substantive process shift. Prior CMS rate review operated largely on a completeness standard: CMS checked that required components were present and that the actuary had documented the reasoning behind key assumptions. The 2026 framework introduces consequence-based review for ILOS specifically, with a formal comment letter mechanism that suspends rate approval until the state provides an adequate data collection plan.

The project timeline implications are significant and have not been widely addressed in trade press coverage of the guide. A state that submits a rate certification in late spring for a July 1 effective date, then receives CMS comment letters in May or June indicating that its ILOS documentation is inadequate, must develop and submit a data collection plan before rates can be finalized. An MCO that has already committed network capacity and staffing resources based on expected capitation levels carries the financial exposure for however long the amendment process takes to resolve. Based on MACPAC's documentation of amendment timelines from the 2023-2024 unwinding period, that exposure can run for several months to most of a year before corrected rates take effect.

The practical implication for actuarial engagements is straightforward: the pre-certification ILOS data inventory needs to happen before the actuarial report is submitted, not after CMS responds. For any state with newly approved ILOS items or expanding ILOS scope, the question of whether state-specific utilization data at the specificity CMS expects actually exists must be answered at the engagement kickoff, with enough lead time to begin data collection if the answer is no. For programs where the ILOS data gap is structural, the actuary's conversation with the state about disclosure, qualification, or deferral to fee-for-service must occur during engagement scoping, not at the certification deadline.

The 5% Rate Range Constraint and the Data Precision Problem

Federal regulations at 42 CFR 438.4(c)(2)(iii) limit the spread between the upper and lower bounds of any certified capitation rate range to no more than 5% of the lower bound. Within that certified range, states may adjust plan capitation by up to 1% during the rating period without resubmitting a certification. The constraint prevents states from certifying artificially wide ranges that mask actuarial uncertainty behind a technically compliant filing.

The design logic inverts under 2026 enrollment conditions. Genuine uncertainty in Medicaid enrollment composition is higher than in a typical certification cycle, because states implementing OBBBA eligibility changes face populations that are actively shifting in ways the base period does not capture. A rate range narrow enough to satisfy the 5% constraint may be narrower than the honest uncertainty band warrants.

The resulting choice: certify within the 5% cap and accept that plan-level renegotiation will likely be necessary if enrollment composition diverges materially, or document the narrow range's limitations explicitly while building amendment triggers into the MCO contract. If actual enrollment falls 8% below certified assumptions rather than the 5% the range accommodates, a new certification process is required before adjusted capitation payments can begin. The unwinding period demonstrated this dynamic directly: KFF documented that states used MLR corridors, risk corridors, and mid-year rate amendments to absorb certification-versus-actual divergences during 2023-2024, with amendment timelines ranging from three to nine months depending on state contract provisions and CMS review queues (KFF, 2024). OBBBA-driven population shifts layer a structurally comparable problem over the still-settling post-redetermination base.

ASOP No. 49 at the Certification Line

ASOP No. 49 Section 3.3 requires the certifying actuary to consider "program changes that are known at the time of the analysis and that are likely to affect the expected costs of the covered population." Three program changes are known at the time of July 2026 certifications: the new MLTSS category documentation requirements, the Appendix B ILOS certification standard, and the OBBBA eligibility changes that will alter enrolled population composition during the rating period. All three must appear in the certification, either as documented adjustments or as disclosed limitations.

The MLTSS change creates procedural exposure. An actuary who certifies a blended MLTSS rate without the category-level supporting documentation the guide now requires is out of compliance with CMS expectations and potentially with ASOP No. 49 Section 3.5 disclosure standards, because the missing category-level analysis is a material component of the certification that the professional cannot simply aggregate away. The ILOS change creates substantive opinion exposure: certifying a cost component where the underlying data does not meet credibility standards requires explicit disclosure of the limitation, the alternative basis used, and the uncertainty range that flows from it. An ILOS Appendix B that simply asserts an estimate without describing the data quality and the professional judgment applied is inadequate on the face of the standard.

Taken together, the 2026-2027 guide raises the minimum floor of what counts as an adequate actuarial certification in Medicaid managed care. States and MCOs accustomed to a documentation bar set primarily by the actuary's professional judgment are now operating against a guide that specifies required deliverables and a CMS review process that treats their absence as grounds for formal comment. Rate certifications signed without explicit population composition adjustment language and disclosed uncertainty ranges create actuarial soundness exposure that will surface in plan financials within one to two quarters of the rating period start, in a program environment where the enrolled population will continue shifting in ways that prior guide cycles were not designed to absorb.