Review Montana TANF standards source hierarchy against ARM 37.78.420

[MaxGhenis]

Context

Axiom source-first encoding of Montana TANF uncovered a source-boundary mismatch with the current PolicyEngine implementation.

The Axiom RuleSpec PR encodes official ARM 37.78.420 from the Montana Administrative Rules corpus as of 2026-07-02:

• RuleSpec PR: Add Montana TANF assistance standards TheAxiomFoundation/rulespec-us#514
• Oracle-classification PR: Classify Montana TANF oracle coverage TheAxiomFoundation/axiom-encode#944
• Source legal ID: us-mt:regulations/title-37/chapter-37-78/subchapter-37-78-4/rule-37-78-420

ARM 37.78.420 contains fixed tables for:

• gross monthly income standards
• net monthly income standards
• benefit standards
• cash assistance payment standards
• TANF Cash Assistance Post-Employment Program payment standards

For example, the encoded ARM table gives a cash assistance payment standard of $401 for a 2-person assistance unit and $504 for a 3-person assistance unit, plus post-employment standards of $375, $275, and $175 for months 1-3.

PolicyEngine currently derives Montana TANF standards from State Plan/manual-style FPG-year/rate parameters. The baseline tests expect, for a 2-person unit in 2024:

• mt_tanf_payment_standard: 575.17
• mt_tanf_benefit_standard: 493.00
• mt_tanf_net_income_standard: 628.03
• mt_tanf_gross_income_standard: 1,161.85

Those come from PE parameters such as:

• gov.states.mt.dhs.tanf.income_standards.payment_fpg_year
• gov.states.mt.dhs.tanf.income_standards.payment_fpg_rate
• gov.states.mt.dhs.tanf.income_standards.benefit_fpg_year
• gov.states.mt.dhs.tanf.income_standards.benefit_fpg_rate

Question

Please review whether PE should treat the State Plan/manual FPG-year/rate source as the current governing source for Montana TANF standards, or whether ARM 37.78.420 remains the controlling source and PE should instead reflect its fixed tables/post-employment branch.

I am not assuming PE is wrong. The issue is that the source hierarchy needs to be explicit before Axiom can claim PE parity for Montana TANF.

Acceptance criteria

• Identify the most upstream current governing source for Montana TANF payment/income standards.
• If PE is correct, document why the State Plan/manual supersedes or operationally controls over the ARM table.
• If ARM 37.78.420 controls, update PE parameters/formulas/tests accordingly.
• Decide whether PE should model the ARM post-employment payment-standard branch.

[MaxGhenis]

Verified correct — no change needed. ARM 37.78.420's fixed dollar table is the stale 2011 amendment (FY2007 FPL); the operative expression is DPHHS TANF 001 Monthly Income Standards (eff. 2025-07-01), issued under that rule's authority, at 35%/30%/30%/30% of the 2023 FPL. PolicyEngine reproduces TANF 001 to the dollar for household sizes 1-3 (2-person: payment $575, benefit $493, NMI $628, GMI $1,162). #8915 dates the TANF 001 references in the two FPL-rate parameters; the ARM post-employment special-case branch ($375/$275/$175) remains unmodeled and can be tracked separately if wanted. 158 MT TANF tests pass unchanged.