diff --git a/changelog.d/wa-cascade-care-savings-exact-fpl-ratio.fixed.md b/changelog.d/wa-cascade-care-savings-exact-fpl-ratio.fixed.md
new file mode 100644
index 00000000000..319a8ed10c7
--- /dev/null
+++ b/changelog.d/wa-cascade-care-savings-exact-fpl-ratio.fixed.md
@@ -0,0 +1 @@
+Decide Washington Cascade Care Savings eligibility on the exact ratio of ACA MAGI to the prior-year poverty guideline instead of the truncated `aca_magi_fraction`, so incomes from 250.003% to 250.994% of the poverty line are no longer eligible (PY2026 and PY2027 Cascade Care Savings Policy, Section 4(1)(c): "Has income up to 250% of the Federal Poverty Level").
diff --git a/policyengine_us/parameters/gov/states/wa/wahbe/cascade_care_savings/fpl_limit.yaml b/policyengine_us/parameters/gov/states/wa/wahbe/cascade_care_savings/fpl_limit.yaml
index f984eff66ed..3105ed41ab0 100644
--- a/policyengine_us/parameters/gov/states/wa/wahbe/cascade_care_savings/fpl_limit.yaml
+++ b/policyengine_us/parameters/gov/states/wa/wahbe/cascade_care_savings/fpl_limit.yaml
@@ -1,7 +1,8 @@
 description: Washington limits income to this share of the federal poverty line under the Cascade Care Savings program.
 values:
   # Eligibility caps household income (ACA MAGI per 26 U.S.C. 36B(d)(2)) at 250%
-  # of the federal poverty line, applied as a "<=" comparison ("up to 250%").
+  # of the federal poverty line, applied as a "<=" comparison ("up to 250%") on
+  # the exact income-to-guideline ratio, not the truncated aca_magi_fraction.
   2026-01-01: 2.5
 
 metadata:
diff --git a/policyengine_us/tests/policy/baseline/gov/states/wa/wahbe/cascade_care_savings/integration.yaml b/policyengine_us/tests/policy/baseline/gov/states/wa/wahbe/cascade_care_savings/integration.yaml
index b4df56fbabc..db7b20ed410 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/wa/wahbe/cascade_care_savings/integration.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/wa/wahbe/cascade_care_savings/integration.yaml
@@ -1,11 +1,13 @@
 # Integration tests for Washington Cascade Care Savings (CCS).
 #
-# These exercise the full chain: aca_magi_fraction (income gate) ->
+# These exercise the full chain: ACA MAGI over the prior-year guideline (income
+# gate, on the exact ratio) ->
 # wa_cascade_care_savings_eligible (Group 1 / Group 3 membership) ->
 # wa_cascade_care_savings (per-member build-up, capped by SLCSP - APTC).
 #
-# slcsp, aca_ptc, and aca_magi_fraction are supplied directly (SLCSP as an annual
-# value) so the arithmetic is fully hand-verifiable. slcsp is a MONTH variable;
+# 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 the
+# arithmetic is fully hand-verifiable. slcsp is a MONTH variable;
 # at the YEAR test period its output is the annual sum (= the value supplied).
 # Each scenario documents the per-member build-up and the cap.
 #
@@ -31,7 +33,9 @@
     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_000
         assigned_aca_ptc: 5_000
@@ -59,7 +63,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.8
+        aca_magi: 18_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 6_000
         aca_ptc: 5_000
         assigned_aca_ptc: 5_000
@@ -91,7 +97,9 @@
     tax_units:
       tax_unit:
         members: [person1, person2]
-        aca_magi_fraction: 2.2
+        aca_magi: 22_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 8_000
         aca_ptc: 7_000
         assigned_aca_ptc: 7_000
@@ -122,7 +130,9 @@
     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
         assigned_aca_ptc: 0
@@ -154,7 +164,9 @@
     tax_units:
       tax_unit:
         members: [person1, person2]
-        aca_magi_fraction: 1.6
+        aca_magi: 16_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 10_000
         aca_ptc: 4_000
         assigned_aca_ptc: 4_000
@@ -184,7 +196,9 @@
     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: 0
         assigned_aca_ptc: 0
@@ -211,7 +225,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.6
+        aca_magi: 26_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 6_000
         aca_ptc: 3_000
         assigned_aca_ptc: 3_000
@@ -254,7 +270,9 @@
     tax_units:
       tax_unit:
         members: [person1, person2, person3, person4]
-        aca_magi_fraction: 1.6
+        aca_magi: 16_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 15_000
         aca_ptc: 6_000
         assigned_aca_ptc: 6_000
@@ -283,7 +301,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.4
+        aca_magi: 14_000
+        tax_unit_fpg:
+          2026: 10_000
         slcsp: 6_000
         aca_ptc: 5_000
         assigned_aca_ptc: 5_000
@@ -322,7 +342,9 @@
     tax_units:
       tax_unit:
         members: [person1, person2]
-        aca_magi_fraction: 1.4
+        aca_magi: 14_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 6_000
         aca_ptc: 5_000
         assigned_aca_ptc: 5_000
@@ -362,7 +384,9 @@
     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_000
         assigned_aca_ptc: 5_000
@@ -394,7 +418,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.6
+        aca_magi: 26_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 12_000
         aca_ptc: 0
         assigned_aca_ptc: 0
diff --git a/policyengine_us/tests/policy/baseline/gov/states/wa/wahbe/cascade_care_savings/wa_cascade_care_savings.yaml b/policyengine_us/tests/policy/baseline/gov/states/wa/wahbe/cascade_care_savings/wa_cascade_care_savings.yaml
index 986ed843771..b64b1d2ea26 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/wa/wahbe/cascade_care_savings/wa_cascade_care_savings.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/wa/wahbe/cascade_care_savings/wa_cascade_care_savings.yaml
@@ -1,9 +1,10 @@
 # Unit tests for the Washington Cascade Care Savings amount.
 #
 # All inputs (is_aca_ptc_eligible / immigration_status /
-# wa_apple_health_expansion_eligible per person, aca_magi_fraction, slcsp as an
-# annual value, aca_ptc) are supplied directly so every expected value is exactly
-# hand-verifiable and independent of the rating-area premium lookup. slcsp is a
+# wa_apple_health_expansion_eligible per person, aca_magi against a prior-year
+# tax_unit_fpg pinned to $10,000, slcsp as an annual value, aca_ptc) are supplied
+# directly so every expected value is exactly hand-verifiable and independent of
+# the rating-area premium lookup. slcsp is a
 # MONTH-period variable; the amount formula annualizes it via
 # add(tax_unit, period, ["slcsp"]). Providing slcsp at the YEAR period sets the
 # annual total, so the values below are annual SLCSP.
@@ -36,7 +37,9 @@
     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_000
     households:
@@ -59,7 +62,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.8
+        aca_magi: 18_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 6_000
         aca_ptc: 5_000
     households:
@@ -82,7 +87,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.0
+        aca_magi: 20_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 6_000
         aca_ptc: 5_000
     households:
@@ -110,7 +117,9 @@
     tax_units:
       tax_unit:
         members: [person1, person2]
-        aca_magi_fraction: 2.2
+        aca_magi: 22_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 8_000
         aca_ptc: 7_000
     households:
@@ -138,7 +147,9 @@
     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: 3_000
     households:
@@ -167,7 +178,9 @@
     tax_units:
       tax_unit:
         members: [person1, person2]
-        aca_magi_fraction: 1.6
+        aca_magi: 16_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 10_000
         aca_ptc: 4_000
     households:
@@ -192,7 +205,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.2
+        aca_magi: 22_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 5_000
         aca_ptc: 5_000
     households:
@@ -216,7 +231,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.6
+        aca_magi: 26_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 6_000
         aca_ptc: 2_000
     households:
@@ -242,7 +259,9 @@
     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:
@@ -264,7 +283,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.0
+        aca_magi: 20_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 6_000
         aca_ptc: 2_000
     households:
@@ -286,7 +307,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.0
+        aca_magi: 20_000
+        tax_unit_fpg:
+          2024: 10_000
         slcsp: 6_000
         aca_ptc: 2_000
     households:
@@ -313,7 +336,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.2
+        aca_magi: 22_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 6_000
         aca_ptc: 5_900
     households:
@@ -337,7 +362,9 @@
     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_340
     households:
@@ -364,7 +391,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.5
+        aca_magi: 15_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 1_000
         aca_ptc: 0
     households:
@@ -389,7 +418,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.51
+        aca_magi: 15_100
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 1_000
         aca_ptc: 0
     households:
@@ -430,7 +461,9 @@
     tax_units:
       tax_unit:
         members: [person1, person2, person3, person4]
-        aca_magi_fraction: 1.6
+        aca_magi: 16_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 15_000
         aca_ptc: 6_000
     households:
@@ -471,7 +504,9 @@
     tax_units:
       tax_unit:
         members: [person1, person2]
-        aca_magi_fraction: 1.4
+        aca_magi: 14_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 6_000
         aca_ptc: 5_000
     households:
@@ -506,7 +541,9 @@
     tax_units:
       tax_unit:
         members: [person1, person2]
-        aca_magi_fraction: 1.4
+        aca_magi: 14_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 12_000
         aca_ptc: 5_000
     households:
@@ -535,7 +572,9 @@
     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_000
     households:
@@ -562,7 +601,9 @@
     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_000
     households:
@@ -590,7 +631,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.4
+        aca_magi: 14_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 12_000
         aca_ptc: 0
     households:
@@ -617,7 +660,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.6
+        aca_magi: 26_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 12_000
         aca_ptc: 0
     households:
@@ -644,7 +689,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.4
+        aca_magi: 14_000
+        tax_unit_fpg:
+          2026: 10_000
         slcsp: 6_000
         aca_ptc: 5_000
     households:
@@ -685,7 +732,9 @@
       tax_unit:
         members: [person1, person2]
         filing_status: SEPARATE
-        aca_magi_fraction: 1.4
+        aca_magi: 14_000
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 12_000
         aca_ptc: 0
     households:
@@ -713,7 +762,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.0001
+        aca_magi: 20_001
+        tax_unit_fpg:
+          2025: 10_000
         slcsp: 1_000
         aca_ptc: 0
     households:
@@ -740,7 +791,9 @@
     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:
diff --git a/policyengine_us/tests/policy/baseline/gov/states/wa/wahbe/cascade_care_savings/wa_cascade_care_savings_eligible.yaml b/policyengine_us/tests/policy/baseline/gov/states/wa/wahbe/cascade_care_savings/wa_cascade_care_savings_eligible.yaml
index b1597e9943e..54c8dac51ed 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/wa/wahbe/cascade_care_savings/wa_cascade_care_savings_eligible.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/wa/wahbe/cascade_care_savings/wa_cascade_care_savings_eligible.yaml
@@ -1,19 +1,23 @@
 # Unit tests for Washington Cascade Care Savings tax-unit eligibility.
 #
 # wa_cascade_care_savings_eligible (TaxUnit, bool) is true when:
-#   in_effect (2026+) AND aca_magi_fraction <= 2.5 (fpl_limit) AND the tax unit
-#   has at least one member in Group 1 or Group 3.
+#   in_effect (2026+) AND aca_magi / prior-year FPG <= 2.5 (fpl_limit; Section
+#   4(1)(c): "up to 250%") AND the tax unit has at least one member in Group 1
+#   or Group 3. The income test uses the exact ratio, not the truncated
+#   aca_magi_fraction.
 #     Group 1: is_aca_ptc_eligible (federally subsidized enrollee).
 #     Group 3: immigration_status == UNDOCUMENTED AND NOT
 #              wa_apple_health_expansion_eligible (undocumented, but not covered
 #              by the Apple Health Expansion Medicaid proxy).
-# All person-level gates and aca_magi_fraction are supplied directly so each
-# expected value is hand-verifiable.
+# All person-level gates are supplied directly. Supplied-income cases pin the
+# prior-year guideline to $10,000 and set aca_magi to the target ratio, so each
+# expected value is hand-verifiable; income-derived cases use the actual 2025
+# one-person guideline, $15,650.
 
 # --- Income limit boundary at 250% FPL (Group 1 member present) ---
 
 - name: Case 1, income just below 250% FPL with a Group 1 member is eligible.
-  # aca_magi_fraction 2.49 <= 2.5 and person1 is Group 1 -> eligible.
+  # 24_900 / 10_000 = 2.49 <= 2.5 and person1 is Group 1 -> eligible.
   period: 2026
   input:
     people:
@@ -23,7 +27,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.49
+        aca_magi: 24_900
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -32,7 +38,7 @@
     wa_cascade_care_savings_eligible: true
 
 - name: Case 2, income exactly at 250% FPL with a Group 1 member is eligible.
-  # aca_magi_fraction 2.5 <= 2.5 (inclusive "up to 250%") -> eligible.
+  # 25_000 / 10_000 = 2.5 <= 2.5 (inclusive "up to 250%") -> eligible.
   period: 2026
   input:
     people:
@@ -42,7 +48,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.5
+        aca_magi: 25_000
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -51,7 +59,7 @@
     wa_cascade_care_savings_eligible: true
 
 - name: Case 3, income just above 250% FPL is ineligible.
-  # aca_magi_fraction 2.51 > 2.5 -> income-ineligible even with a Group 1 member.
+  # 25_100 / 10_000 = 2.51 > 2.5 -> income-ineligible even with a Group 1 member.
   period: 2026
   input:
     people:
@@ -61,7 +69,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.51
+        aca_magi: 25_100
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -69,6 +79,82 @@
   output:
     wa_cascade_care_savings_eligible: false
 
+- name: Case 3a, $39,124 (249.994% 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: 39_124
+    households:
+      household:
+        members: [person1]
+        state_code: WA
+  output:
+    aca_magi_fraction: 2.49
+    wa_cascade_care_savings_eligible: true
+
+- name: Case 3b, $39,125 (exactly 250%) is eligible.
+  period: 2026
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 39_125
+    households:
+      household:
+        members: [person1]
+        state_code: WA
+  output:
+    aca_magi_fraction: 2.50
+    wa_cascade_care_savings_eligible: true
+
+- name: Case 3c, $39,125.47 (250.003%) is ineligible though truncated to 2.50.
+  period: 2026
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 39_125.47
+    households:
+      household:
+        members: [person1]
+        state_code: WA
+  output:
+    aca_magi_fraction: 2.50
+    wa_cascade_care_savings_eligible: false
+
+- name: Case 3d, $39,280.56 (250.994%) is ineligible though truncated to 2.50.
+  period: 2026
+  input:
+    people:
+      person1:
+        age: 40
+        is_aca_ptc_eligible: true
+    tax_units:
+      tax_unit:
+        members: [person1]
+        aca_magi: 39_280.56
+    households:
+      household:
+        members: [person1]
+        state_code: WA
+  output:
+    aca_magi_fraction: 2.50
+    wa_cascade_care_savings_eligible: false
+
 # --- Group membership paths ---
 
 - name: Case 4, undocumented member not Apple-Health-eligible is Group 3, eligible.
@@ -84,7 +170,9 @@
     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]
@@ -106,7 +194,9 @@
     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]
@@ -127,7 +217,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.5
+        aca_magi: 15_000
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -148,7 +240,9 @@
     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]
@@ -167,7 +261,9 @@
     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]
@@ -199,7 +295,9 @@
     tax_units:
       tax_unit:
         members: [person1, person2, person3]
-        aca_magi_fraction: 1.6
+        aca_magi: 16_000
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1, person2, person3]
@@ -227,7 +325,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.4
+        aca_magi: 14_000
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -252,7 +352,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.4
+        aca_magi: 14_000
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -277,7 +379,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 1.4
+        aca_magi: 14_000
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -288,7 +392,7 @@
 - name: Case 9e, income above 250% FPL with a Group-3 member is ineligible.
   # Closes the matrix: prior above-limit cases (Case 3) used a Group 1 member.
   # Here the sole member is Group 3 (UNDOCUMENTED, not Apple-Health-eligible),
-  # is_aca_ptc_eligible false explicitly. aca_magi_fraction 2.51 > 2.5 (fpl_limit)
+  # is_aca_ptc_eligible false explicitly. 25_100 / 10_000 = 2.51 > 2.5 (fpl_limit)
   # -> income-ineligible despite the Group 3 member.
   period: 2026
   input:
@@ -301,7 +405,9 @@
     tax_units:
       tax_unit:
         members: [person1]
-        aca_magi_fraction: 2.51
+        aca_magi: 25_100
+        tax_unit_fpg:
+          2025: 10_000
     households:
       household:
         members: [person1]
@@ -321,7 +427,9 @@
     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]
diff --git a/policyengine_us/variables/gov/states/wa/wahbe/cascade_care_savings/wa_cascade_care_savings_eligible.py b/policyengine_us/variables/gov/states/wa/wahbe/cascade_care_savings/wa_cascade_care_savings_eligible.py
index 55b89a4ad29..d4e8f64cf29 100644
--- a/policyengine_us/variables/gov/states/wa/wahbe/cascade_care_savings/wa_cascade_care_savings_eligible.py
+++ b/policyengine_us/variables/gov/states/wa/wahbe/cascade_care_savings/wa_cascade_care_savings_eligible.py
@@ -14,7 +14,9 @@ class wa_cascade_care_savings_eligible(Variable):
     documentation = (
         "A tax unit is eligible for Cascade Care Savings when the program is "
         "in effect, household income (ACA MAGI per 26 U.S.C. 36B(d)(2)) is at "
-        "or below 250% of the federal poverty line, and at least one member is "
+        "or below 250% of the prior-year federal poverty guideline, measured as "
+        "the exact ratio rather than the truncated aca_magi_fraction, and at "
+        "least one member is "
         "a Cascade Care Savings enrollee (Group 1, eligible for the federal "
         "ACA premium tax credit; or Group 3, undocumented and lacking minimum "
         "essential coverage through Washington Apple Health Expansion or Apple "
@@ -29,8 +31,13 @@ class wa_cascade_care_savings_eligible(Variable):
     def formula(tax_unit, period, parameters):
         p = parameters(period).gov.states.wa.wahbe.cascade_care_savings
         in_effect = p.in_effect
-        magi_fraction = tax_unit("aca_magi_fraction", period)
-        income_eligible = magi_fraction <= p.fpl_limit
+        # Section 4(1)(c) covers income "up to 250% of the Federal Poverty
+        # Level". Test the exact ratio, not the truncated aca_magi_fraction:
+        # truncation maps 250.00%-250.99% to 2.50, which would admit incomes
+        # above 250%.
+        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
         has_eligible_member = (
             add(tax_unit, period, ["wa_cascade_care_savings_member_eligible"]) > 0
         )