MaxGhenis · Oct 20, 2026
diff --git a/changelog.d/vt-premium-assistance-exact-fpl-ratio.fixed.md b/changelog.d/vt-premium-assistance-exact-fpl-ratio.fixed.md
@@ -0,0 +1 @@
+Decide Vermont Premium Assistance eligibility on the exact ratio of ACA MAGI to the prior-year poverty guideline instead of the truncated `aca_magi_fraction`, so incomes from 300.003% to 300.994% of the poverty line are no longer eligible (33 V.S.A. § 1812(a)(1): "less than or equal to 300 percent of federal poverty level").
diff --git a/policyengine_us/tests/policy/baseline/gov/states/vt/dvha/premium_assistance/integration.yaml b/policyengine_us/tests/policy/baseline/gov/states/vt/dvha/premium_assistance/integration.yaml
@@ -56,23 +56,21 @@
     vt_premium_assistance: 585.00
 
 # ---- Scenario 2: full federal derivation, exactly 300% FPL boundary ----
-- name: Scenario 2, single Vermont enrollee at 47k derives exactly 300% FPL and stays eligible.
-  # Raw input: employment_income 47_000. Note the exact 300%/size-1 MAGI is 46_950
-  #   (see vt_premium_assistance.yaml Case 4); 47_000 sits just above it but the
-  #   model still rounds aca_magi_fraction to 3.00, so the inclusive ceiling holds.
-  # Derived: aca_magi = 47_000;
-  #   aca_magi_fraction = 3.00 exactly (the 300% ceiling is inclusive -> eligible);
-  #   fed_pct = 9.96% (start of the 300-400% flat bracket); slcsp = 15_588.
-  # Federal APTC = 15_588 - 47_000*0.0996 = 15_588 - 4_681.20 = 10_906.80.
-  # VPA: fed_pct 9.96% > 1.5% -> gap = 47_000*0.015 = 705.00.
-  #   residual = 15_588 - 10_906.80 = 4_681.20 > gap -> VPA = 705.00.
+- name: Scenario 2, single Vermont enrollee at exactly 300% FPL stays eligible.
+  # Raw input: employment_income 46_950 = 3 x $15,650 (2025 one-person FPG).
+  # Derived: aca_magi = 46_950; aca_magi_fraction = 3.00 exactly (the 300%
+  #   ceiling is inclusive -> eligible); fed_pct = 9.96% (start of the 300-400%
+  #   flat bracket); slcsp = 15_588.
+  # Federal APTC = 15_588 - 46_950*0.0996 = 15_588 - 4_676.22 = 10_911.78.
+  # VPA: fed_pct 9.96% > 1.5% -> gap = 46_950*0.015 = 704.25.
+  #   residual = 15_588 - 10_911.78 = 4_676.22 > gap -> VPA = 704.25.
   period: 2026
   absolute_error_margin: 0.01
   input:
     people:
       person1:
         age: 40
-        employment_income: 47_000
+        employment_income: 46_950
     tax_units:
       tax_unit:
         members: [person1]
@@ -81,14 +79,41 @@
         members: [person1]
         state_code: VT
   output:
-    aca_magi: 47_000
+    aca_magi: 46_950
     aca_magi_fraction: 3.00
     is_aca_ptc_eligible: true
     aca_required_contribution_percentage: 0.0996
     slcsp: 15_588
-    aca_ptc: 10_906.80
+    aca_ptc: 10_911.78
     vt_premium_assistance_eligible: true
-    vt_premium_assistance: 705.00
+    vt_premium_assistance: 704.25
+
+- name: Scenario 2b, single Vermont enrollee at 47k (300.32% FPL) is above the ceiling.
+  # Raw input: employment_income 47_000, which is 300.32% of $15,650. Truncation
+  #   makes aca_magi_fraction 3.00, but 33 V.S.A. 1812(a)(1) covers only income
+  #   "less than or equal to 300 percent", so Vermont Premium Assistance is $0.
+  #   The federal APTC is unaffected: 15_588 - 47_000*0.0996 = 10_906.80.
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 40
+        employment_income: 47_000
+    tax_units:
+      tax_unit:
+        members: [person1]
+    households:
+      household:
+        members: [person1]
+        state_code: VT
+  output:
+    aca_magi: 47_000
+    aca_magi_fraction: 3.00
+    is_aca_ptc_eligible: true
+    aca_ptc: 10_906.80
+    vt_premium_assistance_eligible: false
+    vt_premium_assistance: 0
 
 # ---- Scenario 3: injected, 250% FPL, gap-binding ----
 - name: Scenario 3, 250% FPL injected inputs give a gap-binding VPA of income times 1.5%.
@@ -251,11 +276,11 @@
 # ---- Scenario 8: multi-member household at 300% FPL, gap-binding ----
 - name: Scenario 8, three-person Vermont household at 300% FPL gets a gap-binding VPA scaling with MAGI.
   # A larger family reaches the 300% ceiling at a higher aca_magi, so the gap
-  #   (income * 0.015) scales up. fed_pct at 300% FPL = 9.96% (start of the
-  #   300-400% flat bracket, derived from the injected aca_magi_fraction 3.00).
-  #   income = 100_000 -> gap = 100_000 * 0.015 = 1_500.
+  #   (income * 0.015) scales up. 300% of the 2025 three-person FPG ($26,650) is
+  #   79_950, so aca_magi_fraction = 3.00 and fed_pct = 9.96% (start of the
+  #   300-400% flat bracket). gap = 79_950 * 0.015 = 1_199.25.
   #   residual = slcsp - aca_ptc = 20_000 - 8_000 = 12_000 > gap ->
-  #   VPA = min(1_500, 12_000) = 1_500 (gap binds). Only one member need be
+  #   VPA = min(1_199.25, 12_000) = 1_199.25 (gap binds). Only one member need be
   #   APTC-eligible for the tax unit to qualify at the inclusive 300% ceiling.
   period: 2026
   absolute_error_margin: 0.01
@@ -273,22 +298,21 @@
     tax_units:
       tax_unit:
         members: [person1, person2, person3]
-        aca_magi: 100_000
-        aca_magi_fraction: 3.00
+        aca_magi: 79_950
         slcsp: 20_000
         aca_ptc: 8_000
     households:
       household:
         members: [person1, person2, person3]
         state_code: VT
   output:
-    aca_magi: 100_000
+    aca_magi: 79_950
     aca_magi_fraction: 3.00
     aca_required_contribution_percentage: 0.0996
     slcsp: 20_000
     aca_ptc: 8_000
     vt_premium_assistance_eligible: true
-    vt_premium_assistance: 1_500
+    vt_premium_assistance: 1_199.25
 
 # ---- Scenario 9: full federal derivation, exactly 180% FPL, gap-binding ----
 - name: Scenario 9, single Vermont enrollee at 28.2k derives 180% FPL and gets a gap-binding VPA.

diff --git a/...us/tests/policy/baseline/gov/states/vt/dvha/premium_assistance/vt_premium_assistance.yaml b/...us/tests/policy/baseline/gov/states/vt/dvha/premium_assistance/vt_premium_assistance.yaml
@@ -319,9 +319,10 @@
 
 - name: Case 13, three-person Vermont household at 300% FPL gets a gap scaling with the larger MAGI.
   # A larger family reaches 300% FPL at a higher aca_magi, so the gap
-  # (income * 0.015) scales up accordingly. fed_pct at 300% FPL = 9.96% > 1.5%,
-  # income = 100_000 -> gap = 100_000 * 0.015 = 1_500. residual =
-  # 20_000 - 8_000 = 12_000 > gap, so VPA = 1_500 (gap binds). Eligibility holds
+  # (income * 0.015) scales up accordingly. 300% of the 2025 three-person FPG
+  # ($26,650) is 79_950; fed_pct at 300% FPL = 9.96% > 1.5%, so
+  # gap = 79_950 * 0.015 = 1_199.25. residual = 20_000 - 8_000 = 12_000 > gap,
+  # so VPA = 1_199.25 (gap binds). Eligibility holds
   # at the inclusive 300% ceiling for a multi-member unit, and only one member
   # need be APTC-eligible.
   period: 2026
@@ -340,7 +341,7 @@
     tax_units:
       tax_unit:
         members: [person1, person2, person3]
-        aca_magi: 100_000
+        aca_magi: 79_950
         aca_magi_fraction: 3.00
         slcsp: 20_000
         aca_ptc: 8_000
@@ -349,7 +350,7 @@
         members: [person1, person2, person3]
         state_code: VT
   output:
-    vt_premium_assistance: 1_500
+    vt_premium_assistance: 1_199.25
 
 # ---- Negative MAGI clamp (REQ-12) ----
 

diff --git a/...policy/baseline/gov/states/vt/dvha/premium_assistance/vt_premium_assistance_eligible.yaml b/...policy/baseline/gov/states/vt/dvha/premium_assistance/vt_premium_assistance_eligible.yaml
@@ -1,10 +1,14 @@
 # Unit tests for Vermont Premium Assistance eligibility (REQ-1, REQ-2, REQ-3,
 # REQ-8). A tax unit is eligible when the program is in effect (2026+), at least
 # one member is federal-ACA-PTC-eligible (is_aca_ptc_eligible), and ACA MAGI is
-# at or below 300% of the federal poverty line (aca_magi_fraction <= 3.0).
-#   eligible = in_effect & any(is_aca_ptc_eligible) & (aca_magi_fraction <= 3.0)
-# aca_magi_fraction is injected directly so the 300% boundary is exact and each
-# expectation is hand-verifiable. There is no minimum-income floor.
+# at or below 300% of the federal poverty line (33 V.S.A. 1812(a)(1): "less
+# than or equal to 300 percent"), on the exact ratio of ACA MAGI to the
+# prior-year guideline, not the truncated aca_magi_fraction:
+#   eligible = in_effect & any(is_aca_ptc_eligible) & (aca_magi / FPG <= 3.0)
+# Supplied-income cases pin the prior-year guideline to $10,000 and set
+# aca_magi to the target ratio, so each expectation is hand-verifiable.
+# Income-derived cases use the actual 2025 one-person guideline, $15,650.
+# There is no minimum-income floor.
 
 - name: Case 1, 250% FPL APTC-eligible Vermont tax unit is eligible.
   # in_effect (2026) true; member APTC-eligible; 2.50 <= 3.0 -> eligible.
@@ -17,7 +21,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.50
+        aca_magi: 25_000
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -36,7 +42,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.99
+        aca_magi: 29_900
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -55,7 +63,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 3.00
+        aca_magi: 30_000
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -74,7 +84,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 3.01
+        aca_magi: 30_100
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -93,7 +105,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.50
+        aca_magi: 25_000
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -115,7 +129,9 @@
     tax_units:
       tax_unit:
         members: [person1, person2]
-        aca_magi_fraction: 2.50
+        aca_magi: 25_000
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1, person2]
@@ -134,7 +150,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.50
+        aca_magi: 25_000
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -153,7 +171,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.50
+        aca_magi: 25_000
+        tax_unit_fpg:
+          2024: 10_000
     households:
       household:
         members: [person1]
@@ -172,7 +192,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.50
+        aca_magi: 25_000
+        tax_unit_fpg:
+          2026: 10_000
     households:
       household:
         members: [person1]
@@ -181,7 +203,7 @@
     vt_premium_assistance_eligible: true
 
 - name: Case 10, 300.01% FPL just barely above the ceiling is ineligible.
-  # 3.0001 > 3.0 -> ineligible. Tightest just-above-ceiling case (REQ-2 boundary),
+  # 30_001 / 10_000 = 3.0001 > 3.0 -> ineligible. Tightest just-above-ceiling case (REQ-2 boundary),
   # complementing the inclusive 3.00 eligible case and the coarser 3.01 case.
   period: 2026
   input:
@@ -192,10 +214,89 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 3.0001
+        aca_magi: 30_001
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
         state_code: VT
   output:
     vt_premium_assistance_eligible: false
+
+- name: Case 11, $46,950 (exactly 300% of the 2025 guideline) is eligible.
+  # 3 x $15,650 = $46,950; aca_magi_fraction 3.00.
+  period: 2026
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 46_950
+    households:
+      household:
+        members: [person1]
+        state_code: VT
+  output:
+    aca_magi_fraction: 3.00
+    vt_premium_assistance_eligible: true
+
+- name: Case 12, $46,950.47 (300.003%) is ineligible though truncated to 3.00.
+  period: 2026
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 46_950.47
+    households:
+      household:
+        members: [person1]
+        state_code: VT
+  output:
+    aca_magi_fraction: 3.00
+    vt_premium_assistance_eligible: false
+
+- name: Case 13, $47,105.56 (300.994%) is ineligible though truncated to 3.00.
+  period: 2026
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 47_105.56
+    households:
+      household:
+        members: [person1]
+        state_code: VT
+  output:
+    aca_magi_fraction: 3.00
+    vt_premium_assistance_eligible: false
+
+- name: Case 14, $46,949 (299.994%) is eligible.
+  period: 2026
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 46_949
+    households:
+      household:
+        members: [person1]
+        state_code: VT
+  output:
+    aca_magi_fraction: 2.99
+    vt_premium_assistance_eligible: true
diff --git a/...gine_us/variables/gov/states/vt/dvha/premium_assistance/vt_premium_assistance_eligible.py b/...gine_us/variables/gov/states/vt/dvha/premium_assistance/vt_premium_assistance_eligible.py
@@ -17,7 +17,9 @@ class vt_premium_assistance_eligible(Variable):
         "premium tax credit (which embeds on-Marketplace enrollment, the "
         "married-filing-separately exclusion, and the federal required-"
         "contribution income test), and household income is at or below 300% of "
-        "the federal poverty line. Vermont imposes no minimum-income floor, so "
+        "the federal poverty line, measured as the exact ratio of ACA MAGI to "
+        "the prior-year guideline rather than the truncated aca_magi_fraction. "
+        "Vermont imposes no minimum-income floor, so "
         "the low end is governed by the federal PTC gate, including its below-"
         "poverty immigration exception, which Vermont inherits rather than "
         "overrides."
@@ -28,6 +30,11 @@ def formula(tax_unit, period, parameters):
         in_effect = p.in_effect
         # At least one member must be eligible for the federal ACA PTC.
         aptc_eligible = tax_unit.any(tax_unit.members("is_aca_ptc_eligible", period))
-        magi_fraction = tax_unit("aca_magi_fraction", period)
-        income_eligible = magi_fraction <= p.fpl_limit
+        # 33 V.S.A. 1812(a)(1) covers income "less than or equal to 300
+        # percent of federal poverty level". Test the exact ratio, not the
+        # truncated aca_magi_fraction: truncation maps 300.00%-300.99% to
+        # 3.00, which would admit incomes above 300%.
+        magi = max_(tax_unit("aca_magi", period), 0)
+        exact_magi_frac = magi / tax_unit("tax_unit_fpg", period.last_year)
+        income_eligible = exact_magi_frac <= p.fpl_limit
         return in_effect & aptc_eligible & income_eligible
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Decide Vermont Premium Assistance eligibility on the exact ratio of ACA MAGI to the prior-year poverty guideline instead of the truncated `aca_magi_fraction`, so incomes from 300.003% to 300.994% of the poverty line are no longer eligible (33 V.S.A. § 1812(a)(1): "less than or equal to 300 percent of federal poverty level").