diff --git a/changelog.d/ma-connectorcare-exact-fpl-ratio.fixed.md b/changelog.d/ma-connectorcare-exact-fpl-ratio.fixed.md
new file mode 100644
index 00000000000..def0a650264
--- /dev/null
+++ b/changelog.d/ma-connectorcare-exact-fpl-ratio.fixed.md
@@ -0,0 +1 @@
+Decide Massachusetts ConnectorCare's income ceiling and Plan Type bands on the exact ratio of ACA MAGI to the prior-year poverty guideline instead of the truncated `aca_magi_fraction`. 956 CMR 12.04(3)(b) puts income "at or below 150%" in Plan Type 2A, "over 150% and not over 200%" in 2B, and so on up to 3C, "not over 400%"; truncation put incomes from 150.003% to 150.994% (and the same slivers above 200%, 250% and 300%) in the cheaper band below. The 400% ceiling changes results only under a reform that extends the federal credit above 400%.
diff --git a/policyengine_us/parameters/gov/states/ma/hic/connector_care/enrollee_premium.yaml b/policyengine_us/parameters/gov/states/ma/hic/connector_care/enrollee_premium.yaml
index 6ce38ca508e..2cbf3a4b104 100644
--- a/policyengine_us/parameters/gov/states/ma/hic/connector_care/enrollee_premium.yaml
+++ b/policyengine_us/parameters/gov/states/ma/hic/connector_care/enrollee_premium.yaml
@@ -16,41 +16,44 @@ metadata:
       href: https://www.mahealthconnector.org/wp-content/uploads/amended-956CMR12.00.pdf#page=13
 
 brackets:
-  # Household income measured as ACA MAGI as a share of the federal poverty line.
-  # Band boundaries are lower-exclusive / upper-inclusive per 956 CMR 12.04(3)(b),
-  # so thresholds use the "x.0001" convention matching the published "150.1%"
-  # banding. The schedule is a flat dollar step function decoupled from the
-  # affordability percent-of-income schedule (Board-set, 956 CMR 12.12(9)); every
-  # band is $0 before the PY2026 effective date.
-  # Plan Type 2A, 100-150% FPL -> $0 per person per month.
+  # Household income measured as ACA MAGI as a share of the prior-year federal
+  # poverty guideline, the exact ratio. Band boundaries are lower-exclusive /
+  # upper-inclusive per 956 CMR 12.04(3)(b) ("at or below 150%", "over 150% and
+  # not over 200%"), so each threshold is the band's lower edge and
+  # ma_connector_care evaluates the scale with right-closed brackets: a ratio
+  # exactly at a threshold stays in the band below it. The schedule is a flat
+  # dollar step function decoupled from the affordability percent-of-income
+  # schedule (Board-set, 956 CMR 12.12(9)); every band is $0 before the PY2026
+  # effective date.
+  # Plan Type 2A, 100% to 150% FPL -> $0 per person per month.
   - threshold:
       2026-01-01: 1
     amount:
       0000-01-01: 0
       2026-01-01: 0
-  # Plan Type 2B, 150.1-200% FPL -> $53.
+  # Plan Type 2B, over 150% to 200% FPL -> $53.
   - threshold:
-      2026-01-01: 1.5001
+      2026-01-01: 1.5
     amount:
       0000-01-01: 0
       2026-01-01: 53
-  # Plan Type 3A, 200.1-250% FPL -> $103.
+  # Plan Type 3A, over 200% to 250% FPL -> $103.
   - threshold:
-      2026-01-01: 2.0001
+      2026-01-01: 2
     amount:
       0000-01-01: 0
       2026-01-01: 103
-  # Plan Type 3B, 250.1-300% FPL -> $152.
+  # Plan Type 3B, over 250% to 300% FPL -> $152.
   - threshold:
-      2026-01-01: 2.5001
+      2026-01-01: 2.5
     amount:
       0000-01-01: 0
       2026-01-01: 152
-  # Plan Type 3C, 300.1-400% FPL -> $235. This tier is a pilot extended through
+  # Plan Type 3C, over 300% to 400% FPL -> $235. This tier is a pilot extended through
   # FY2026 in the state budget and may lapse in out-years; it is carried forward
   # without end-dating as a current-law assumption.
   - threshold:
-      2026-01-01: 3.0001
+      2026-01-01: 3
     amount:
       0000-01-01: 0
       2026-01-01: 235
diff --git a/policyengine_us/tests/policy/baseline/gov/states/ma/hic/connector_care/integration.yaml b/policyengine_us/tests/policy/baseline/gov/states/ma/hic/connector_care/integration.yaml
index f3f18d6f8c4..aea4744dc8b 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/ma/hic/connector_care/integration.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/ma/hic/connector_care/integration.yaml
@@ -1,12 +1,14 @@
 # Integration tests for Massachusetts ConnectorCare (PY2026 premium wrap).
 #
-# These exercise the full chain: aca_magi_fraction (income gate) and
+# These exercise the full chain: the exact ratio of ACA MAGI to the prior-year
+# guideline (income gate and Plan Type band) and
 # is_aca_ptc_eligible (member gate) -> ma_connector_care_member_eligible ->
 # ma_connector_care_eligible -> ma_connector_care (residual subsidy) ->
 # healthcare_benefit_value (household resource aggregation).
 #
-# In Scenarios 1-5 slcsp, aca_ptc, and aca_magi_fraction are supplied directly
-# (slcsp as an annual value) so every expected value is fully hand-verifiable.
+# In Scenarios 1-5 slcsp and aca_ptc are supplied directly (slcsp as an annual
+# value), and income is aca_magi against a prior-year tax_unit_fpg pinned to
+# $10,000, so every expected value is fully hand-verifiable.
 # slcsp is a MONTH variable; supplying it at the YEAR period sets the annual sum.
 # Scenario 6 instead derives aca_magi_fraction, aca_ptc, and is_aca_ptc_eligible
 # from raw employment_income (only slcsp is supplied), per the Code Integrity note
@@ -20,12 +22,12 @@
 #
 # Amount formula recap:
 #   n_members      = count of ma_connector_care_member_eligible (= is_aca_ptc_eligible)
-#   per_person_mo  = enrollee_premium.calc(aca_magi_fraction)   # single_amount bracket
+#   per_person_mo  = enrollee_premium.calc(ACA MAGI / prior-year FPG, right=True)
 #   contribution   = 12 * per_person_mo * n_members
 #   subsidy        = max(0, slcsp_annual - aca_ptc - contribution)
 #   amount         = where(ma_connector_care_eligible, subsidy, 0)
-# Bracket (per person per month): [1.0,1.5001)->0, [1.5001,2.0001)->53,
-#   [2.0001,2.5001)->103, [2.5001,3.0001)->152, [3.0001,inf)->235.
+# Bracket (per person per month, right-closed): [1.0,1.5]->0, (1.5,2.0]->53,
+#   (2.0,2.5]->103, (2.5,3.0]->152, (3.0,inf)->235.
 
 - name: Scenario 1, single adult at 175% FPL, band 2B ($53/mo), positive residual.
   # n_members=1, band 2B -> per_person 53. contribution = 12*53 = 636.
@@ -40,7 +42,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.75
+        aca_magi: 17_500
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 7_200
         aca_ptc: 5_000
         assigned_aca_ptc: 5_000
@@ -68,7 +72,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.4
+        aca_magi: 14_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 6_000
         aca_ptc: 5_500
         assigned_aca_ptc: 5_500
@@ -100,7 +106,9 @@
     tax_units:
       tax_unit:
         members: [person1, person2]
-        aca_magi_fraction: 1.75
+        aca_magi: 17_500
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 7_200
         aca_ptc: 5_000
         assigned_aca_ptc: 5_000
@@ -129,7 +137,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 3.5
+        aca_magi: 35_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 8_000
         aca_ptc: 4_000
         assigned_aca_ptc: 4_000
@@ -159,7 +169,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 3.5
+        aca_magi: 35_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 5_000
         aca_ptc: 3_000
         assigned_aca_ptc: 3_000
@@ -221,7 +233,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.75
+        aca_magi: 17_500
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 7_200
         aca_ptc: 5_000
         assigned_aca_ptc: 5_000
@@ -261,7 +275,9 @@
     tax_units:
       tax_unit:
         members: [person1, person2, person3, person4, person5]
-        aca_magi_fraction: 3.5
+        aca_magi: 35_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 20_000
         aca_ptc: 0
         assigned_aca_ptc: 0
diff --git a/policyengine_us/tests/policy/baseline/gov/states/ma/hic/connector_care/ma_connector_care.yaml b/policyengine_us/tests/policy/baseline/gov/states/ma/hic/connector_care/ma_connector_care.yaml
index cf046cd4d31..a3866f9f00f 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/ma/hic/connector_care/ma_connector_care.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/ma/hic/connector_care/ma_connector_care.yaml
@@ -2,24 +2,31 @@
 #
 # ma_connector_care (TaxUnit, YEAR, USD, defined_for StateCode.MA):
 #   n_members         = count of ma_connector_care_member_eligible (= is_aca_ptc_eligible)
-#   per_person_month  = enrollee_premium.calc(aca_magi_fraction)   # single_amount bracket
+#   ratio             = max(aca_magi, 0) / tax_unit_fpg(prior year)  # exact, not truncated
+#   per_person_month  = enrollee_premium.calc(ratio, right=True)   # single_amount bracket
 #   contribution      = MONTHS_IN_YEAR (12) * per_person_month * n_members
 #   slcsp_annual      = add(tax_unit, period, ["slcsp"])           # MONTH var summed to year
 #   subsidy           = max(0, slcsp_annual - aca_ptc - contribution)
 #   amount            = where(ma_connector_care_eligible, subsidy, 0)
 #
-# All of slcsp / aca_ptc / aca_magi_fraction / is_aca_ptc_eligible are supplied
-# directly so each expected value is hand-verifiable. slcsp is a MONTH variable;
+# slcsp / aca_ptc / is_aca_ptc_eligible are supplied directly, and income is
+# aca_magi against a prior-year tax_unit_fpg pinned to $10,000, so each expected
+# value is hand-verifiable. Income-derived cases at the end use the actual 2025
+# one-person guideline, $15,650. slcsp is a MONTH variable;
 # supplying it at the YEAR period sets the annual total, so the values below are
 # annual SLCSP.
 #
-# Per-person monthly enrollee premium bracket (single_amount, lower-exclusive):
-#   [1.0, 1.5001)  -> $0     (Plan Type 2A)
-#   [1.5001, 2.0001) -> $53  (Plan Type 2B)
-#   [2.0001, 2.5001) -> $103 (Plan Type 3A)
-#   [2.5001, 3.0001) -> $152 (Plan Type 3B)
-#   [3.0001, ...)  -> $235   (Plan Type 3C)
-# So at EXACTLY 150%/200%/250%/300% FPL the household is still in the LOWER band.
+# Per-person monthly enrollee premium bracket (single_amount, evaluated
+# right-closed; 956 CMR 12.04(3)(b): "at or below 150%", "over 150% and not over
+# 200%", ...):
+#   [1.0, 1.5]  -> $0     (Plan Type 2A)
+#   (1.5, 2.0]  -> $53    (Plan Type 2B)
+#   (2.0, 2.5]  -> $103   (Plan Type 3A)
+#   (2.5, 3.0]  -> $152   (Plan Type 3B)
+#   (3.0, 4.0]  -> $235   (Plan Type 3C)
+# So at EXACTLY 150%/200%/250%/300% FPL the household is still in the LOWER band,
+# and any income above an edge is in the higher band, even below the next whole
+# percentage point.
 
 # --- Each band exercised with a positive residual, single member (n=1) ---
 
@@ -35,7 +42,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.4
+        aca_magi: 14_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 6_000
         aca_ptc: 5_500
     households:
@@ -57,7 +66,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.75
+        aca_magi: 17_500
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 7_200
         aca_ptc: 5_000
     households:
@@ -79,7 +90,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.25
+        aca_magi: 22_500
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 9_000
         aca_ptc: 5_000
     households:
@@ -101,7 +114,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.75
+        aca_magi: 27_500
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 9_000
         aca_ptc: 4_000
     households:
@@ -123,7 +138,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 3.5
+        aca_magi: 35_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 8_000
         aca_ptc: 4_000
     households:
@@ -149,7 +166,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.5
+        aca_magi: 15_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 12_000
         aca_ptc: 0
     households:
@@ -171,7 +190,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.51
+        aca_magi: 15_100
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 12_000
         aca_ptc: 0
     households:
@@ -193,7 +214,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.0
+        aca_magi: 20_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 12_000
         aca_ptc: 0
     households:
@@ -215,7 +238,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.01
+        aca_magi: 20_100
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 12_000
         aca_ptc: 0
     households:
@@ -237,7 +262,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.5
+        aca_magi: 25_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 12_000
         aca_ptc: 0
     households:
@@ -259,7 +286,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.51
+        aca_magi: 25_100
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 12_000
         aca_ptc: 0
     households:
@@ -281,7 +310,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 3.0
+        aca_magi: 30_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 12_000
         aca_ptc: 0
     households:
@@ -303,7 +334,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 3.01
+        aca_magi: 30_100
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 12_000
         aca_ptc: 0
     households:
@@ -331,7 +364,9 @@
     tax_units:
       tax_unit:
         members: [person1, person2]
-        aca_magi_fraction: 1.75
+        aca_magi: 17_500
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 7_200
         aca_ptc: 5_000
     households:
@@ -357,7 +392,9 @@
     tax_units:
       tax_unit:
         members: [person1, person2]
-        aca_magi_fraction: 2.25
+        aca_magi: 22_500
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 9_000
         aca_ptc: 5_000
     households:
@@ -380,7 +417,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 3.5
+        aca_magi: 35_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 5_000
         aca_ptc: 3_000
     households:
@@ -402,7 +441,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.0
+        aca_magi: 20_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 9_000
         aca_ptc: 0
     households:
@@ -424,7 +465,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.4
+        aca_magi: 14_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 6_000
         aca_ptc: 0
     households:
@@ -446,7 +489,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.4
+        aca_magi: 14_000
+        tax_unit_fpg:
+          2024: 10_000
         slcsp: 6_000
         aca_ptc: 0
     households:
@@ -472,7 +517,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.4
+        aca_magi: 14_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 0
         aca_ptc: 0
     households:
@@ -497,7 +544,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.75
+        aca_magi: 17_500
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 5_636
         aca_ptc: 5_000
     households:
@@ -533,7 +582,9 @@
     tax_units:
       tax_unit:
         members: [person1, person2, person3, person4, person5]
-        aca_magi_fraction: 3.5
+        aca_magi: 35_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 20_000
         aca_ptc: 0
     households:
@@ -557,7 +608,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.0
+        aca_magi: 10_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 6_000
         aca_ptc: 5_500
     households:
@@ -566,3 +619,210 @@
         state_code: MA
   output:
     ma_connector_care: 500
+
+- name: Case 24, 150% of the 2025 guideline ($23,475) is Plan Type 2A ($0/mo).
+  # contribution = 12*0*1 = 0. subsidy = 9_000 - 5_000 - 0 = 4_000.
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 23_475
+        slcsp: 9_000
+        aca_ptc: 5_000
+    households:
+      household:
+        members: [person1]
+        state_code: MA
+  output:
+    aca_magi_fraction: 1.50
+    ma_connector_care: 4_000
+
+- name: Case 25, 150.003% of the 2025 guideline ($23,475.47) is Plan Type 2B ($53/mo).
+  # contribution = 12*53*1 = 636. subsidy = 9_000 - 5_000 - 636 = 3_364.
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 23_475.47
+        slcsp: 9_000
+        aca_ptc: 5_000
+    households:
+      household:
+        members: [person1]
+        state_code: MA
+  output:
+    aca_magi_fraction: 1.50
+    ma_connector_care: 3_364
+
+- name: Case 26, 150.994% of the 2025 guideline ($23,630.56) is Plan Type 2B ($53/mo).
+  # contribution = 12*53*1 = 636. subsidy = 9_000 - 5_000 - 636 = 3_364.
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 23_630.56
+        slcsp: 9_000
+        aca_ptc: 5_000
+    households:
+      household:
+        members: [person1]
+        state_code: MA
+  output:
+    aca_magi_fraction: 1.50
+    ma_connector_care: 3_364
+
+- name: Case 27, 200% of the 2025 guideline ($31,300) is Plan Type 2B ($53/mo).
+  # contribution = 12*53*1 = 636. subsidy = 9_000 - 5_000 - 636 = 3_364.
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 31_300
+        slcsp: 9_000
+        aca_ptc: 5_000
+    households:
+      household:
+        members: [person1]
+        state_code: MA
+  output:
+    aca_magi_fraction: 2.00
+    ma_connector_care: 3_364
+
+- name: Case 28, 200.003% of the 2025 guideline ($31,300.47) is Plan Type 3A ($103/mo).
+  # contribution = 12*103*1 = 1_236. subsidy = 9_000 - 5_000 - 1_236 = 2_764.
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 31_300.47
+        slcsp: 9_000
+        aca_ptc: 5_000
+    households:
+      household:
+        members: [person1]
+        state_code: MA
+  output:
+    aca_magi_fraction: 2.00
+    ma_connector_care: 2_764
+
+- name: Case 29, 250% of the 2025 guideline ($39,125) is Plan Type 3A ($103/mo).
+  # contribution = 12*103*1 = 1_236. subsidy = 9_000 - 5_000 - 1_236 = 2_764.
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 39_125
+        slcsp: 9_000
+        aca_ptc: 5_000
+    households:
+      household:
+        members: [person1]
+        state_code: MA
+  output:
+    aca_magi_fraction: 2.50
+    ma_connector_care: 2_764
+
+- name: Case 30, 250.003% of the 2025 guideline ($39,125.47) is Plan Type 3B ($152/mo).
+  # contribution = 12*152*1 = 1_824. subsidy = 9_000 - 5_000 - 1_824 = 2_176.
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 39_125.47
+        slcsp: 9_000
+        aca_ptc: 5_000
+    households:
+      household:
+        members: [person1]
+        state_code: MA
+  output:
+    aca_magi_fraction: 2.50
+    ma_connector_care: 2_176
+
+- name: Case 31, 300% of the 2025 guideline ($46,950) is Plan Type 3B ($152/mo).
+  # contribution = 12*152*1 = 1_824. subsidy = 9_000 - 5_000 - 1_824 = 2_176.
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 46_950
+        slcsp: 9_000
+        aca_ptc: 5_000
+    households:
+      household:
+        members: [person1]
+        state_code: MA
+  output:
+    aca_magi_fraction: 3.00
+    ma_connector_care: 2_176
+
+- name: Case 32, 300.003% of the 2025 guideline ($46,950.47) is Plan Type 3C ($235/mo).
+  # contribution = 12*235*1 = 2_820. subsidy = 9_000 - 5_000 - 2_820 = 1_180.
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 46_950.47
+        slcsp: 9_000
+        aca_ptc: 5_000
+    households:
+      household:
+        members: [person1]
+        state_code: MA
+  output:
+    aca_magi_fraction: 3.00
+    ma_connector_care: 1_180
diff --git a/policyengine_us/tests/policy/baseline/gov/states/ma/hic/connector_care/ma_connector_care_eligible.yaml b/policyengine_us/tests/policy/baseline/gov/states/ma/hic/connector_care/ma_connector_care_eligible.yaml
index 0ce81de5955..09774b0c94f 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/ma/hic/connector_care/ma_connector_care_eligible.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/ma/hic/connector_care/ma_connector_care_eligible.yaml
@@ -2,18 +2,23 @@
 #
 # ma_connector_care_eligible (TaxUnit, YEAR, bool, defined_for StateCode.MA) is:
 #   in_effect
-#   & (aca_magi_fraction >= fpl_floor)      # fpl_floor = 1.0 for PY2026
-#   & (aca_magi_fraction <= fpl_limit)      # fpl_limit = 4.0 for PY2026
+#   & (ratio >= fpl_floor)      # fpl_floor = 1.0 for PY2026
+#   & (ratio <= fpl_limit)      # fpl_limit = 4.0 for PY2026 (956 CMR 12.04(3)(b):
+#                               # Plan Type 3C is "not over 400% of the FPL")
+# where ratio = max(aca_magi, 0) / tax_unit_fpg(prior year), the exact ratio, not
+# the truncated aca_magi_fraction.
 #   & (count of ma_connector_care_member_eligible members > 0)
 #
 # ma_connector_care_member_eligible = is_aca_ptc_eligible (Person, YEAR).
 # in_effect is false before 2026-01-01, true from 2026-01-01 open-ended.
-# aca_magi_fraction is supplied directly so the income band is exact.
+# Supplied-income cases pin the prior-year guideline to $10,000 and set aca_magi
+# to the target ratio; income-derived cases use the 2025 one-person guideline,
+# $15,650.
 
 # --- Income-band boundaries at the 100% FPL floor (>= comparison) ---
 
 - name: Case 1, one APTC-eligible member just below the 100% FPL floor is ineligible.
-  # aca_magi_fraction 0.99 < fpl_floor 1.0 -> income_eligible false.
+  # ratio 0.99 < fpl_floor 1.0 -> income_eligible false.
   period: 2026
   input:
     people:
@@ -23,7 +28,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 0.99
+        aca_magi: 9_900
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -32,7 +39,7 @@
     ma_connector_care_eligible: false
 
 - name: Case 2, one APTC-eligible member exactly at the 100% FPL floor is eligible.
-  # aca_magi_fraction 1.0 >= fpl_floor 1.0 (inclusive) and <= 4.0 -> eligible.
+  # ratio 1.0 >= fpl_floor 1.0 (inclusive) and <= 4.0 -> eligible.
   period: 2026
   input:
     people:
@@ -42,7 +49,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.0
+        aca_magi: 10_000
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -53,7 +62,7 @@
 # --- Income-band boundaries at the 400% FPL limit (<= comparison) ---
 
 - name: Case 3, one APTC-eligible member exactly at the 400% FPL limit is eligible.
-  # aca_magi_fraction 4.0 <= fpl_limit 4.0 (inclusive) -> eligible.
+  # ratio 4.0 <= fpl_limit 4.0 (inclusive) -> eligible.
   period: 2026
   input:
     people:
@@ -63,7 +72,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 4.0
+        aca_magi: 40_000
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -72,7 +83,7 @@
     ma_connector_care_eligible: true
 
 - name: Case 4, one APTC-eligible member just above the 400% FPL limit is ineligible.
-  # aca_magi_fraction 4.01 > fpl_limit 4.0 -> income_eligible false.
+  # ratio 4.01 > fpl_limit 4.0 -> income_eligible false.
   period: 2026
   input:
     people:
@@ -82,7 +93,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 4.01
+        aca_magi: 40_100
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -93,7 +106,7 @@
 # --- Member and residency gates ---
 
 - name: Case 5, in-band household with no APTC-eligible member is ineligible.
-  # aca_magi_fraction 2.0 is in band but has_eligible_member is false.
+  # ratio 2.0 is in band but has_eligible_member is false.
   period: 2026
   input:
     people:
@@ -103,7 +116,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.0
+        aca_magi: 20_000
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -122,7 +137,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.0
+        aca_magi: 20_000
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -143,7 +160,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.0
+        aca_magi: 20_000
+        tax_unit_fpg:
+          2024: 10_000
     households:
       household:
         members: [person1]
@@ -162,10 +181,96 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.0
+        aca_magi: 20_000
+        tax_unit_fpg:
+          2026: 10_000
     households:
       household:
         members: [person1]
         state_code: MA
   output:
     ma_connector_care_eligible: true
+
+- name: Case 9, $62,600 (exactly 400% of the 2025 guideline) is eligible.
+  period: 2026
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 62_600
+    households:
+      household:
+        members: [person1]
+        state_code: MA
+  output:
+    aca_magi_fraction: 4.00
+    ma_connector_care_eligible: true
+
+- name: Case 10, $62,600.47 (400.003%) is ineligible though truncated to 4.00.
+  period: 2026
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 62_600.47
+    households:
+      household:
+        members: [person1]
+        state_code: MA
+  output:
+    aca_magi_fraction: 4.00
+    ma_connector_care_eligible: false
+
+- name: Case 11, $62,755.56 (400.994%) is ineligible though truncated to 4.00.
+  period: 2026
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 62_755.56
+    households:
+      household:
+        members: [person1]
+        state_code: MA
+  output:
+    aca_magi_fraction: 4.00
+    ma_connector_care_eligible: false
+
+- name: Case 12, with the federal credit extended above 400%, 400.003% is still ineligible.
+  # A reform that keeps the premium tax credit above 400% FPL makes the member
+  # APTC-eligible at $62,600.47, so the ConnectorCare ceiling alone decides.
+  period: 2026
+  input:
+    gov.aca.ptc_income_eligibility[2].amount: true
+    people:
+      person1:
+        age: 40
+        is_medicaid_eligible: false
+        is_chip_eligible: false
+        is_basic_health_program_eligible: false
+        is_aca_eshi_eligible: false
+        is_medicare_eligible: false
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 62_600.47
+        filing_status: SINGLE
+    households:
+      household:
+        members: [person1]
+        state_code: MA
+  output:
+    is_aca_ptc_eligible: [true]
+    ma_connector_care_eligible: false
diff --git a/policyengine_us/variables/gov/states/ma/hic/connector_care/ma_connector_care.py b/policyengine_us/variables/gov/states/ma/hic/connector_care/ma_connector_care.py
index 154b1faf3d2..6d57f10d1bc 100644
--- a/policyengine_us/variables/gov/states/ma/hic/connector_care/ma_connector_care.py
+++ b/policyengine_us/variables/gov/states/ma/hic/connector_care/ma_connector_care.py
@@ -45,8 +45,14 @@ class ma_connector_care(Variable):
     def formula(tax_unit, period, parameters):
         p = parameters(period).gov.states.ma.hic.connector_care
         n_members = add(tax_unit, period, ["ma_connector_care_member_eligible"])
-        magi_fraction = tax_unit("aca_magi_fraction", period)
-        per_person_monthly = p.enrollee_premium.calc(magi_fraction)
+        # 956 CMR 12.04(3)(b) assigns Plan Types by exact income bands that
+        # include their upper edge: "at or below 150%" is 2A, "over 150% and
+        # not over 200%" is 2B, and so on. Look up the exact ratio, not the
+        # truncated aca_magi_fraction (which put 150.00%-150.99% in 2A), with
+        # each bracket closed on the right.
+        magi = max_(tax_unit("aca_magi", period), 0)
+        exact_magi_frac = magi / tax_unit("tax_unit_fpg", period.last_year)
+        per_person_monthly = p.enrollee_premium.calc(exact_magi_frac, right=True)
         enrollee_contribution = MONTHS_IN_YEAR * per_person_monthly * n_members
         # SLCSP is a MONTH variable summed to the year to proxy the benchmark
         # ConnectorCare plan; the full APTC is netted per 956 CMR 12.04(3)(c).
diff --git a/policyengine_us/variables/gov/states/ma/hic/connector_care/ma_connector_care_eligible.py b/policyengine_us/variables/gov/states/ma/hic/connector_care/ma_connector_care_eligible.py
index a138a04a40e..3ce513c376b 100644
--- a/policyengine_us/variables/gov/states/ma/hic/connector_care/ma_connector_care_eligible.py
+++ b/policyengine_us/variables/gov/states/ma/hic/connector_care/ma_connector_care_eligible.py
@@ -16,8 +16,10 @@ class ma_connector_care_eligible(Variable):
     documentation = (
         "A tax unit is eligible for ConnectorCare when the program is in "
         "effect, household income (ACA MAGI per 26 U.S.C. 36B(d)(2)) as a "
-        "share of the federal poverty line is at or above the 100% FPL floor "
-        "and at or below the 400% FPL limit (the operational 2026 band), and "
+        "share of the prior-year federal poverty guideline, measured as the "
+        "exact ratio rather than the truncated aca_magi_fraction, is at or "
+        "above the 100% FPL floor and at or below the 400% FPL limit (the "
+        "operational 2026 band), and "
         "at least one member is eligible for the federal ACA premium tax "
         "credit. Massachusetts residency is enforced by defined_for. The "
         "amended 956 CMR still defines a sub-100% Plan Type 1 and a 400.1-500% "
@@ -29,9 +31,14 @@ class ma_connector_care_eligible(Variable):
     def formula(tax_unit, period, parameters):
         p = parameters(period).gov.states.ma.hic.connector_care
         in_effect = p.in_effect
-        magi_fraction = tax_unit("aca_magi_fraction", period)
-        income_eligible = (magi_fraction >= p.fpl_floor) & (
-            magi_fraction <= p.fpl_limit
+        # 956 CMR 12.04(3)(b) bounds Plan Type 3C by income "not over 400% of
+        # the FPL". Test the exact ratio, not the truncated aca_magi_fraction:
+        # truncation maps 400.00%-400.99% to 4.00, which would admit incomes
+        # above 400%. The floor ("at least 100%") is unaffected by truncation.
+        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_floor) & (
+            exact_magi_frac <= p.fpl_limit
         )
         has_eligible_member = (
             add(tax_unit, period, ["ma_connector_care_member_eligible"]) > 0