Model working-disabled Medicaid buy-in as one Medicaid category with state-specific parameters

[daphnehanse11]

PolicyEngine should model working-disabled Medicaid buy-in pathways as one shared Medicaid eligibility category with state-specific parameters, rather than as dozens of independent state programs.

Background

KFF 2026 State Health Facts marks 47 states as having Medicaid buy-in pathways for working people with disabilities. Illinois HBWD is already implemented state-specifically, and Mississippi has a separate issue (#8441), but the remaining state-specific tickets created in #8446-#8491 showed that most differences are parameter data rather than fundamentally different logic.

Sources:

• KFF State Health Facts, Medicaid Eligibility Through Buy-In Programs for Working People with Disabilities: https://www.kff.org/medicaid/state-indicator/medicaid-eligibility-through-buy-in-programs-for-working-people-with-disabilities/
• MACPAC, Medicaid Buy-In Pathways: https://www.macpac.gov/medicaid-buy-in-pathways/
• CMS, Ticket to Work / Medicaid Buy-In: https://www.medicaid.gov/medicaid/long-term-services-supports/medicaid-employment-initiatives/ticket-work

Repetition found

Across the 45 state-specific issues filed from the KFF table:

• 19 states use a 250% FPL income limit.
• 6 states have no income standard reported.
• 9 states have no asset limit.
• 15 states have no age limit reported.
• 14 states have no premium/monthly fee reported or applicable.

The common shape is:

disabled + working + state resident + income test + asset test + optional age test + optional premium.

Proposed architecture

Add a shared Medicaid category/pathway, tentatively:

gov.hhs.medicaid.eligibility.categories.working_disabled_buy_in

Add a new Medicaid category enum value, e.g. WORKING_DISABLED_BUY_IN, rather than folding this into SENIOR_OR_DISABLED, because premiums and downstream health/spending analysis need to distinguish buy-in eligibility.

Suggested variables:

• is_working_disabled_buy_in_for_medicaid
• is_working_disabled_buy_in_income_eligible
• is_working_disabled_buy_in_asset_eligible
• is_working_disabled_buy_in_age_eligible
• is_working_disabled_buy_in_employment_eligible
• working_disabled_buy_in_medicaid_premium or integration into a broader medicaid_premium framework

Suggested state-breakdown parameters:

• in_effect.yaml
• income/fpl_limit/individual.yaml
• income/fpl_limit/couple.yaml
• income/monthly_limit/individual.yaml and /couple.yaml if needed for states where the table/source gives dollar limits directly
• assets/limit/individual.yaml
• assets/limit/couple.yaml
• age/min.yaml
• age/max.yaml
• work/monthly_hours_threshold.yaml where applicable
• premium parameters for fixed-dollar, range, percent-of-income, and capped premium formulas

State-specific escape hatches

Default to the shared pathway. Add state-specific variables only where source rules cannot be parameterized cleanly, for example:

• Mississippi's earned/unearned split and 40-hour rule (Model Mississippi Working Disabled Medicaid buy-in pathway #8441).
• Rhode Island's multiple subpathways.
• New Hampshire's MEAD/MOAD split.
• Massachusetts CommonHealth-specific behavior.
• Complex premium schedules that do not fit the first shared premium schema.

Illinois HBWD can either remain as a state-specific implementation initially or be migrated into the shared category once the shared schema is stable.

Acceptance criteria

• Add WORKING_DISABLED_BUY_IN (or equivalent) to Medicaid category handling.
• Add shared eligibility variables and state-breakdown parameters for the common buy-in tests.
• Integrate the shared pathway into is_medicaid_eligible and Medicaid cost/category logic.
• Add at least a representative test matrix:
  • one 250% FPL state,
  • one no-asset-limit state,
  • one state with a fixed premium,
  • one state with an age limit,
  • one state with no income standard reported.
• Document which states are covered by the shared schema and which still require state-specific follow-up.
• Avoid creating 45 separate state program implementations for rules that fit the shared schema.

Replaces state-specific tickets

This issue replaces the state-by-state tickets #8446 through #8491, excluding unrelated issue #8453. Those tickets should be closed in favor of this shared implementation approach.

Related: #8363, #1011, #8441, #8102, #6010.