diff --git a/changelog.d/cdcc-coupling-accuracy.fixed.md b/changelog.d/cdcc-coupling-accuracy.fixed.md
new file mode 100644
index 00000000000..6073bebc3fe
--- /dev/null
+++ b/changelog.d/cdcc-coupling-accuracy.fixed.md
@@ -0,0 +1,4 @@
+- Honored the IRC § 21(e)(4) separated-taxpayer exception in the South Carolina child and dependent care credit.
+- Stopped the Idaho and Georgia contributed child tax credit reforms from applying in years before their in_effect activation date.
+- Computed the Kentucky, Maine, and Vermont child and dependent care credits from the pre-OBBBA federal IRC § 21 credit for 2026, matching each state's static conformity to the Internal Revenue Code as of December 31, 2024.
+- Reduced the California, Idaho, and Virginia child and dependent care benefit bases by employer-provided dependent care benefits excluded under IRC § 129, matching each state's form treatment and the federal IRC § 21(c) reduction.
diff --git a/policyengine_us/reforms/states/ga/ctc/ga_ctc_reform.py b/policyengine_us/reforms/states/ga/ctc/ga_ctc_reform.py
index 74b942341c9..6ff5bf1eb8a 100644
--- a/policyengine_us/reforms/states/ga/ctc/ga_ctc_reform.py
+++ b/policyengine_us/reforms/states/ga/ctc/ga_ctc_reform.py
@@ -40,7 +40,12 @@ def formula(tax_unit, period, parameters):
             ga_child_age_eligible = age < baseline.age_threshold
             eligible_children = tax_unit.sum(ctc_eligible_child & ga_child_age_eligible)
             refund_limit = p.refundable.amount * eligible_children
-            return min_(unused_credit, refund_limit)
+            refundable_credit = min_(unused_credit, refund_limit)
+            # Only pay the refund in periods where the reform is in effect. The
+            # reform is installed for the whole simulation whenever it activates
+            # in any of the next five years (see create_ga_ctc_reform), so this
+            # per-period gate prevents a refund leaking into pre-activation years.
+            return where(p.refundable.in_effect, refundable_credit, 0)
 
     class ga_refundable_credits(Variable):
         value_type = float
diff --git a/policyengine_us/reforms/states/id/ctc/id_ctc_reform.py b/policyengine_us/reforms/states/id/ctc/id_ctc_reform.py
index 26dcd81c9bb..771d5c45848 100644
--- a/policyengine_us/reforms/states/id/ctc/id_ctc_reform.py
+++ b/policyengine_us/reforms/states/id/ctc/id_ctc_reform.py
@@ -6,6 +6,24 @@
 )
 
 
+def _first_true_instant(nodes, default):
+    """Earliest instant at which any of the boolean parameters is true.
+
+    Scans each parameter's ``values_list`` (which reflects user-supplied dated
+    overrides) for the earliest instant whose value is truthy, and returns the
+    minimum such instant across all nodes. Falls back to ``default`` when none
+    of the parameters is ever true.
+    """
+    candidates = []
+    for node in nodes:
+        for value_at_instant in node.values_list:
+            if value_at_instant.value:
+                candidates.append(instant(value_at_instant.instant_str))
+    if not candidates:
+        return default
+    return min(candidates)
+
+
 def create_id_ctc() -> Reform:
     class id_refundable_ctc(Variable):
         value_type = float
@@ -40,22 +58,38 @@ def formula(tax_unit, period, parameters):
             return where(p.refundable.in_effect, refundable_credit, 0)
 
     def modify_parameters(parameters):
-        # Revive id_ctc in the ordered nonrefundable list (it was dropped as of
-        # 2026), so the baseline credit applies against liability again.
+        # The baseline id_ctc drops out of the ordered nonrefundable list as of
+        # 2026-01-01. Revive it only from the instant the reform actually turns
+        # on, so a delayed activation does not leak the credit into
+        # pre-activation years. The activation instant is the earliest date at
+        # which either in_effect toggle is true; default to 2026-01-01 (the
+        # baseline drop date) when neither carries a dated override.
+        p_id = parameters.gov.contrib.states.id.ctc
+        baseline_drop = instant("2026-01-01")
+        activation = _first_true_instant(
+            [p_id.in_effect, p_id.refundable.in_effect],
+            default=baseline_drop,
+        )
+        # Never revive before the baseline drop date: id_ctc is already in the
+        # list through 2025, so revival only matters from 2026 onward.
+        revival_start = max(activation, baseline_drop)
         non_refundable = parameters.gov.states.id.tax.income.credits.non_refundable
-        current_non_refundable = non_refundable(instant("2026-01-01"))
+        current_non_refundable = non_refundable(revival_start)
         if "id_ctc" not in current_non_refundable:
             non_refundable.update(
-                start=instant("2026-01-01"),
+                start=revival_start,
                 stop=instant("2100-12-31"),
                 value=list(current_non_refundable) + ["id_ctc"],
             )
-        # Register the refundable top-up in the refundable list.
+        # Register the refundable top-up in the refundable list. The
+        # id_refundable_ctc variable self-gates on refundable.in_effect, so it
+        # pays nothing before activation; registering it from the same revival
+        # instant keeps the list free of a dead entry in pre-activation years.
         refundable = parameters.gov.states.id.tax.income.credits.refundable
-        current_refundable = refundable(instant("2026-01-01"))
+        current_refundable = refundable(revival_start)
         if "id_refundable_ctc" not in current_refundable:
             refundable.update(
-                start=instant("2026-01-01"),
+                start=revival_start,
                 stop=instant("2100-12-31"),
                 value=list(current_refundable) + ["id_refundable_ctc"],
             )
diff --git a/policyengine_us/tests/policy/baseline/gov/irs/credits/cdcc/pre_obbba_cdcc.yaml b/policyengine_us/tests/policy/baseline/gov/irs/credits/cdcc/pre_obbba_cdcc.yaml
new file mode 100644
index 00000000000..1806d204ca7
--- /dev/null
+++ b/policyengine_us/tests/policy/baseline/gov/irs/credits/cdcc/pre_obbba_cdcc.yaml
@@ -0,0 +1,67 @@
+# The pre_obbba_cdcc family recomputes the federal section 21 credit on the
+# rate schedule as it stood before the One Big Beautiful Bill Act (OBBBA). For
+# 2025 it must equal the live cdcc (identical schedule); for 2026 it must hold
+# the pre-OBBBA rate (max 35%, min 20%, no amended second phase-out) while the
+# live cdcc reflects the OBBBA increase (max 50%, min 35%). Read by states whose
+# income tax statically conforms to a pre-2026 IRC (KY, ME, VT).
+
+# Low-income joint family, two children, $6,000 childcare, AGI below the first
+# phase-out start so the applicable rate is at its maximum.
+- name: 2025 pre-OBBBA CDCC equals the live CDCC (identical schedule)
+  period: 2025
+  absolute_error_margin: 0.01
+  input:
+    people:
+      head:
+        age: 35
+        employment_income: 25_000
+      spouse:
+        age: 35
+        employment_income: 25_000
+      child1:
+        age: 5
+      child2:
+        age: 7
+    tax_units:
+      tax_unit:
+        members: [head, spouse, child1, child2]
+        filing_status: JOINT
+        tax_unit_childcare_expenses: 6_000
+        premium_tax_credit: 0
+  output:
+    # $6,000 x 20% applicable rate at this AGI = $1,200 (same as live cdcc).
+    cdcc: 1_200
+    pre_obbba_cdcc_potential: 1_200
+    pre_obbba_cdcc: 1_200
+    pre_obbba_capped_cdcc: 1_200
+
+- name: 2026 pre-OBBBA CDCC holds the pre-OBBBA rate while live CDCC rises
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      head:
+        age: 35
+        employment_income: 25_000
+      spouse:
+        age: 35
+        employment_income: 25_000
+      child1:
+        age: 5
+      child2:
+        age: 7
+    tax_units:
+      tax_unit:
+        members: [head, spouse, child1, child2]
+        filing_status: JOINT
+        tax_unit_childcare_expenses: 6_000
+        premium_tax_credit: 0
+  output:
+    # Live 2026 credit uses the OBBBA rate (35% here) = $2,100 potential,
+    # $1,780 after the section 26 cap for this family.
+    cdcc_potential: 2_100
+    cdcc: 1_780
+    # Pre-OBBBA credit holds the 20% pre-OBBBA rate = $1,200.
+    pre_obbba_cdcc_potential: 1_200
+    pre_obbba_cdcc: 1_200
+    pre_obbba_capped_cdcc: 1_200
diff --git a/policyengine_us/tests/policy/baseline/gov/states/ca/tax/income/credits/child_dependent_care/ca_cdcc_relevant_expenses.yaml b/policyengine_us/tests/policy/baseline/gov/states/ca/tax/income/credits/child_dependent_care/ca_cdcc_relevant_expenses.yaml
index 582dd6df1fc..8f099dd7295 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/ca/tax/income/credits/child_dependent_care/ca_cdcc_relevant_expenses.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/ca/tax/income/credits/child_dependent_care/ca_cdcc_relevant_expenses.yaml
@@ -72,3 +72,18 @@
     # One qualifying individual at the pre-ARPA $3,000 cap:
     # min(10_000 adult care, 3_000, 50_000) = 3_000.
     ca_cdcc_relevant_expenses: 3_000
+
+# FTB 3506 Part IV reduces the $3,000 / $6,000 dollar limit by the IRC § 129
+# employer-provided dependent care benefits excluded from income, matching the
+# federal § 21(c) reduction.
+- name: Section 129 employer benefits reduce the California base
+  period: 2024
+  input:
+    state_code: CA
+    tax_unit_childcare_expenses: 10_000
+    count_cdcc_eligible: 2
+    min_head_spouse_earned: 50_000
+    dependent_care_assistance_exclusion: 5_000
+  output:
+    # min(10_000 expenses, $6,000 two-child cap - $5,000 exclusion, 50_000) = 1_000.
+    ca_cdcc_relevant_expenses: 1_000
diff --git a/policyengine_us/tests/policy/baseline/gov/states/id/tax/income/deductions/household_and_dependent_care/id_household_and_dependent_care_expense_deduction.yaml b/policyengine_us/tests/policy/baseline/gov/states/id/tax/income/deductions/household_and_dependent_care/id_household_and_dependent_care_expense_deduction.yaml
index 79457d953dd..f02284f9c08 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/id/tax/income/deductions/household_and_dependent_care/id_household_and_dependent_care_expense_deduction.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/id/tax/income/deductions/household_and_dependent_care/id_household_and_dependent_care_expense_deduction.yaml
@@ -109,3 +109,18 @@
     state_code: ID
   output:
     id_household_and_dependent_care_expense_deduction: 3_000
+
+# Idaho Form 39R Line 6 worksheet line 4 reduces the operative cap by the IRC
+# § 129 employer-provided dependent care benefits ("excluded benefits from Part
+# III of Form 2441"). Here the reduced $12,000 cap binds below the expenses.
+- name: Section 129 employer benefits reduce the Idaho deduction cap
+  period: 2023
+  input:
+    tax_unit_childcare_expenses: 10_000
+    id_cdcc_limit: 6_000
+    min_head_spouse_earned: 60_000
+    dependent_care_assistance_exclusion: 5_000
+    state_code: ID
+  output:
+    # min(10_000 expenses, max(6_000, 12_000) - 5_000 = 7_000, 60_000) = 7_000.
+    id_household_and_dependent_care_expense_deduction: 7_000
diff --git a/policyengine_us/tests/policy/baseline/gov/states/ky/tax/income/credits/dependent_care_credit/ky_cdcc.yaml b/policyengine_us/tests/policy/baseline/gov/states/ky/tax/income/credits/dependent_care_credit/ky_cdcc.yaml
index 203d68b36a8..e57c2abaa4b 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/ky/tax/income/credits/dependent_care_credit/ky_cdcc.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/ky/tax/income/credits/dependent_care_credit/ky_cdcc.yaml
@@ -20,3 +20,39 @@
     ky_tuition_tax_credit: 0
   output:
     ky_cdcc: 0
+
+# KRS 141.010(21) freezes Kentucky's IRC at December 31, 2024, so from 2026 the
+# credit uses the pre-OBBBA federal section 21 credit (20% of $1,200 = $240),
+# not the OBBBA-inflated live credit (which would give 20% of $1,780 = $356).
+- name: 2026 uses the pre-OBBBA federal credit under static conformity
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      head:
+        age: 35
+        employment_income: 25_000
+      spouse:
+        age: 35
+        employment_income: 25_000
+      child1:
+        age: 5
+      child2:
+        age: 7
+    tax_units:
+      tax_unit:
+        members: [head, spouse, child1, child2]
+        filing_status: JOINT
+        tax_unit_childcare_expenses: 6_000
+        premium_tax_credit: 0
+        ky_income_tax_before_non_refundable_credits_unit: 1_000_000
+        ky_personal_tax_credits: 0
+        ky_family_size_tax_credit: 0
+        ky_tuition_tax_credit: 0
+    households:
+      household:
+        members: [head, spouse, child1, child2]
+        state_code: KY
+  output:
+    # 20% of the pre-OBBBA $1,200 federal credit.
+    ky_cdcc: 240
diff --git a/policyengine_us/tests/policy/baseline/gov/states/me/tax/income/credits/child_care_credit.yaml b/policyengine_us/tests/policy/baseline/gov/states/me/tax/income/credits/child_care_credit.yaml
index cac68bcba34..d3de3601bf5 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/me/tax/income/credits/child_care_credit.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/me/tax/income/credits/child_care_credit.yaml
@@ -59,3 +59,21 @@
     me_child_care_credit: 750
     me_refundable_child_care_credit: 500
     me_non_refundable_child_care_credit: 250
+
+# 36 M.R.S. § 111(1-A) freezes Maine's "Code" at December 31, 2024, so from 2026
+# the credit is 25% of the pre-OBBBA federal credit (pre_obbba_cdcc), not the
+# OBBBA-inflated live cdcc. Inject both to confirm the pin reads the frozen
+# variable.
+- name: 2026 uses the pre-OBBBA federal credit under static conformity
+  period: 2026
+  absolute_error_margin: 0
+  input:
+    state_code: ME
+    filing_status: SINGLE
+    cdcc: 4_000
+    pre_obbba_cdcc: 1_000
+    me_step_4_share_of_child_care_expenses: 0
+    me_income_tax_before_credits: 1_000_000
+  output:
+    # 25% of the frozen $1,000, ignoring the $4,000 live credit.
+    me_child_care_credit: 250
diff --git a/policyengine_us/tests/policy/baseline/gov/states/sc/tax/income/credits/sc_cdcc.yaml b/policyengine_us/tests/policy/baseline/gov/states/sc/tax/income/credits/sc_cdcc.yaml
index ece99500f3e..41efc4c120a 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/sc/tax/income/credits/sc_cdcc.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/sc/tax/income/credits/sc_cdcc.yaml
@@ -79,3 +79,60 @@
     sc_income_tax_before_non_refundable_credits: 1000000
   output:
     sc_cdcc: 210
+
+# S.C. Code § 12-6-3380 computes the credit "as provided in Internal Revenue
+# Code Section 21," importing § 21(e)(2)'s joint-return rule together with the
+# § 21(e)(4) separated-taxpayer exception. An ordinary married-separate filer
+# remains ineligible; a separated filer who lives apart while maintaining a home
+# for a qualifying individual qualifies, matching the federal treatment.
+- name: Ordinary married-filing-separately filer gets no SC CDCC
+  period: 2024
+  input:
+    people:
+      head:
+        age: 35
+        is_tax_unit_head: true
+        employment_income: 40_000
+      child:
+        age: 5
+        is_tax_unit_head: false
+        is_tax_unit_spouse: false
+    tax_units:
+      tax_unit:
+        members: [head, child]
+        filing_status: SEPARATE
+        cdcc_relevant_expenses: 3_000
+        sc_income_tax_before_non_refundable_credits: 1_000_000
+    households:
+      household:
+        members: [head, child]
+        state_code: SC
+  output:
+    sc_cdcc: 0
+
+- name: Separated MFS filer maintaining a home for a qualifying child gets the SC CDCC
+  period: 2024
+  input:
+    people:
+      head:
+        age: 35
+        is_tax_unit_head: true
+        is_separated: true
+        employment_income: 40_000
+      child:
+        age: 5
+        is_tax_unit_head: false
+        is_tax_unit_spouse: false
+    tax_units:
+      tax_unit:
+        members: [head, child]
+        filing_status: SEPARATE
+        cdcc_relevant_expenses: 3_000
+        sc_income_tax_before_non_refundable_credits: 1_000_000
+    households:
+      household:
+        members: [head, child]
+        state_code: SC
+  output:
+    # 7% of min($3,000 spent, $3,000 one-person 2024 cap) = $210.
+    sc_cdcc: 210
diff --git a/policyengine_us/tests/policy/baseline/gov/states/va/tax/income/deductions/cdcc_expense/va_child_dependent_care_deduction_cdcc_limit.yaml b/policyengine_us/tests/policy/baseline/gov/states/va/tax/income/deductions/cdcc_expense/va_child_dependent_care_deduction_cdcc_limit.yaml
index d285bf0c4a1..f5a01e7f762 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/va/tax/income/deductions/cdcc_expense/va_child_dependent_care_deduction_cdcc_limit.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/va/tax/income/deductions/cdcc_expense/va_child_dependent_care_deduction_cdcc_limit.yaml
@@ -13,3 +13,26 @@
     state_code: VA
   output:
     va_child_dependent_care_deduction_cdcc_limit: 3_000
+
+# Va. Code § 58.1-322.03(3) deducts the amount on which the federal credit is
+# based (Form 2441 line 31), which IRC § 21(c) reduces by § 129 employer
+# benefits. The Virginia limit inherits that reduction.
+- name: Section 129 employer benefits reduce the Virginia limit
+  period: 2024
+  input:
+    capped_count_cdcc_eligible: 2
+    dependent_care_assistance_exclusion: 5_000
+    state_code: VA
+  output:
+    # $6,000 two-child limit less the $5,000 exclusion.
+    va_child_dependent_care_deduction_cdcc_limit: 1_000
+
+- name: Section 129 benefits exceeding the limit floor it at zero
+  period: 2024
+  input:
+    capped_count_cdcc_eligible: 1
+    dependent_care_assistance_exclusion: 5_000
+    state_code: VA
+  output:
+    # max($3,000 - $5,000, 0) = $0.
+    va_child_dependent_care_deduction_cdcc_limit: 0
diff --git a/policyengine_us/tests/policy/baseline/gov/states/vt/tax/income/credits/cdcc/vt_cdcc.yaml b/policyengine_us/tests/policy/baseline/gov/states/vt/tax/income/credits/cdcc/vt_cdcc.yaml
index 9a7a5c687df..8551b964dac 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/vt/tax/income/credits/cdcc/vt_cdcc.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/vt/tax/income/credits/cdcc/vt_cdcc.yaml
@@ -41,3 +41,17 @@
     state_code: VT
   output:
     vt_cdcc: 720
+
+# 32 V.S.A. § 5824 freezes Vermont's IRC at December 31, 2024, so from 2026 the
+# credit is 72% of the pre-OBBBA federal credit (pre_obbba_capped_cdcc), not the
+# OBBBA-inflated live capped_cdcc. Inject both to confirm the pin reads the
+# frozen variable.
+- name: Vermont CDCC 2026 uses the pre-OBBBA federal credit under static conformity
+  period: 2026
+  input:
+    capped_cdcc: 2_000
+    pre_obbba_capped_cdcc: 1_000
+    state_code: VT
+  output:
+    # 72% of the frozen $1,000, ignoring the $2,000 live credit.
+    vt_cdcc: 720
diff --git a/policyengine_us/tests/policy/contrib/states/test_id_ga_ctc_reform_activation.py b/policyengine_us/tests/policy/contrib/states/test_id_ga_ctc_reform_activation.py
new file mode 100644
index 00000000000..91f4d035358
--- /dev/null
+++ b/policyengine_us/tests/policy/contrib/states/test_id_ga_ctc_reform_activation.py
@@ -0,0 +1,132 @@
+"""Regression tests for the Idaho and Georgia CTC contributed reforms under a
+DELAYED ``in_effect`` activation date (PolicyEngine/policyengine-us#8899).
+
+The YAML tests for these reforms can only set contrib parameters as scalars
+(one value for every period), so they cannot express "``in_effect`` turns on in
+2028" and never exercised the pre-activation years. Two leaks hid behind that
+gap:
+
+* ``ga_refundable_ctc`` had no per-period ``in_effect`` gate, so once the reform
+  was installed (the factory installs it for the whole simulation whenever the
+  toggle is true in any of the next five years) it paid the refund in every
+  year, including pre-activation ones.
+* the Idaho reform's ``modify_parameters`` revived ``id_ctc`` in the ordered
+  nonrefundable list from a hardcoded ``2026-01-01`` regardless of the actual
+  activation date, so the revived nonrefundable credit applied before the
+  reform turned on.
+
+These tests drive a multi-year simulation with the toggle set true only from
+2028 and assert the reform is inert in the 2026 pre-activation year and active
+in 2028.
+"""
+
+from policyengine_core.periods import instant
+from policyengine_core.reforms import Reform
+
+from policyengine_us import Simulation
+
+ACTIVATION_YEAR = "2028-01-01"
+
+
+def _activate_from_2028(param_path):
+    """A user reform that sets the given boolean contrib parameter true from
+    2028 onward (mirroring how the app applies a contrib toggle)."""
+
+    class ActivateFrom2028(Reform):
+        def apply(self):
+            def modify(parameters):
+                node = parameters
+                for part in param_path.split("."):
+                    node = getattr(node, part)
+                node.update(
+                    start=instant(ACTIVATION_YEAR),
+                    stop=instant("2100-12-31"),
+                    value=True,
+                )
+                return parameters
+
+            self.modify_parameters(modify)
+
+    return ActivateFrom2028
+
+
+GA_SITUATION = {
+    "people": {
+        "parent": {"age": {"2026": 30, "2028": 30}},
+        "child": {
+            "age": {"2026": 2, "2028": 4},
+            "ctc_qualifying_child": {"2026": True, "2028": True},
+        },
+    },
+    "tax_units": {
+        "tax_unit": {
+            "members": ["parent", "child"],
+            "filing_status": {"2026": "SINGLE", "2028": "SINGLE"},
+            "ga_income_tax_before_non_refundable_credits": {"2026": 0, "2028": 0},
+        }
+    },
+    "households": {
+        "household": {
+            "members": ["parent", "child"],
+            "state_code": {"2026": "GA", "2028": "GA"},
+        }
+    },
+}
+
+ID_SITUATION = {
+    "people": {
+        "parent": {"age": {"2026": 30, "2028": 30}},
+        "child1": {
+            "age": {"2026": 2, "2028": 4},
+            "ctc_qualifying_child": {"2026": True, "2028": True},
+        },
+        "child2": {
+            "age": {"2026": 4, "2028": 6},
+            "ctc_qualifying_child": {"2026": True, "2028": True},
+        },
+    },
+    "tax_units": {
+        "tax_unit": {
+            "members": ["parent", "child1", "child2"],
+            "filing_status": {"2026": "SINGLE", "2028": "SINGLE"},
+            "id_income_tax_before_non_refundable_credits": {
+                "2026": 1_000,
+                "2028": 1_000,
+            },
+        }
+    },
+    "households": {
+        "household": {
+            "members": ["parent", "child1", "child2"],
+            "state_code": {"2026": "ID", "2028": "ID"},
+        }
+    },
+}
+
+
+def _simulation(situation, param_path):
+    # start_instant must be the earliest simulated year so the structural-reform
+    # factory sees the full window (this is the documented start_instant patch).
+    return Simulation(
+        situation=situation,
+        reform=_activate_from_2028(param_path),
+        start_instant="2026-01-01",
+    )
+
+
+def test__ga_refundable_ctc_does_not_leak_before_activation():
+    sim = _simulation(GA_SITUATION, "gov.contrib.states.ga.ctc.refundable.in_effect")
+    # Pre-activation (2026): no refund.
+    assert sim.calculate("ga_refundable_ctc", 2026)[0] == 0
+    # Activation year (2028): full $250 per-child refund pays out.
+    assert sim.calculate("ga_refundable_ctc", 2028)[0] == 250
+
+
+def test__id_ctc_revival_does_not_leak_before_activation():
+    sim = _simulation(ID_SITUATION, "gov.contrib.states.id.ctc.in_effect")
+    # id_ctc always computes the worksheet amount (2 * 205 = 410)...
+    assert sim.calculate("id_ctc", 2026)[0] == 410
+    # ...but the revival must NOT apply it in the pre-activation year.
+    assert sim.calculate("id_non_refundable_credits", 2026)[0] == 0
+    # In the activation year the revived nonrefundable credit applies.
+    assert sim.calculate("id_non_refundable_credits", 2028)[0] == 410
diff --git a/policyengine_us/variables/gov/irs/credits/cdcc/pre_obbba_cdcc.py b/policyengine_us/variables/gov/irs/credits/cdcc/pre_obbba_cdcc.py
new file mode 100644
index 00000000000..90d52da4f6a
--- /dev/null
+++ b/policyengine_us/variables/gov/irs/credits/cdcc/pre_obbba_cdcc.py
@@ -0,0 +1,86 @@
+from policyengine_us.model_api import *
+
+
+class pre_obbba_cdcc_potential(Variable):
+    value_type = float
+    entity = TaxUnit
+    label = "Federal CDCC before the section 26 cap, pre-OBBBA section 21 rate"
+    documentation = (
+        "The federal child and dependent care credit before the section 26 "
+        "liability cap, recomputed with the IRC section 21 rate schedule as it "
+        "stood before the One Big Beautiful Bill Act (OBBBA). States whose "
+        "income tax statically conforms to a pre-2026 IRC read this instead of "
+        "the live federal credit so they do not silently adopt the OBBBA "
+        "section 21 rate increase, effective for tax years beginning after "
+        "2025-12-31."
+    )
+    unit = USD
+    definition_period = YEAR
+    reference = "https://www.law.cornell.edu/uscode/text/26/21#a_2"
+
+    def formula(tax_unit, period, parameters):
+        # Only the section 21(a)(2) rate schedule changed under OBBBA
+        # (phase_out.max 0.35->0.50, phase_out.min 0.20->0.35, plus a new
+        # amended second phase-out), all dated 2026-01-01. The section 21(b)-(e)
+        # expense base is unchanged, so freeze only the rate by reading the cdcc
+        # parameter subtree at a pre-OBBBA instant. Any 2023-2025 instant yields
+        # the same schedule; use 2025-01-01. The pre-OBBBA schedule has no
+        # second phase-out after 2021 (second_start is infinite from 2022), so
+        # the first phase-out is the whole rate computation.
+        frozen = parameters("2025-01-01").gov.irs.credits.cdcc
+        agi = tax_unit("adjusted_gross_income", period)
+        excess_agi = max_(0, agi - frozen.phase_out.start)
+        increments = np.ceil(excess_agi / frozen.phase_out.increment)
+        percentage_reduction = increments * frozen.phase_out.rate
+        rate = max_(
+            frozen.phase_out.min,
+            frozen.phase_out.max - percentage_reduction,
+        )
+        eligible = tax_unit("cdcc_filing_status_eligible", period)
+        expenses = tax_unit("cdcc_relevant_expenses", period)
+        return eligible * expenses * rate
+
+
+class pre_obbba_cdcc(Variable):
+    value_type = float
+    entity = TaxUnit
+    label = "Federal CDCC (section 26 non-refundable cap), pre-OBBBA section 21 rate"
+    documentation = (
+        "Mirror of the live cdcc variable but built on the pre-OBBBA section 21 "
+        "rate schedule, for states whose income tax statically conforms to a "
+        "pre-2026 IRC."
+    )
+    unit = USD
+    definition_period = YEAR
+    reference = "https://www.law.cornell.edu/uscode/text/26/21"
+
+    def formula(tax_unit, period, parameters):
+        # cdcc has been non-refundable since 2022; every state that reads this
+        # computes post-2022, so apply the section 26 liability cap directly
+        # (the refundable-2021 branch of the live cdcc is not reachable here).
+        potential = tax_unit("pre_obbba_cdcc_potential", period)
+        credit_limit = tax_unit("cdcc_credit_limit", period)
+        return min_(credit_limit, potential)
+
+
+class pre_obbba_capped_cdcc(Variable):
+    value_type = float
+    entity = TaxUnit
+    label = "Capped federal CDCC (Credit Limit Worksheet), pre-OBBBA section 21 rate"
+    documentation = (
+        "Mirror of the live capped_cdcc variable but built on the pre-OBBBA "
+        "section 21 rate schedule, for states whose income tax statically "
+        "conforms to a pre-2026 IRC."
+    )
+    unit = USD
+    definition_period = YEAR
+    reference = "https://www.irs.gov/instructions/i2441"
+
+    def formula(tax_unit, period, parameters):
+        cdcc = tax_unit("pre_obbba_cdcc", period)
+        # 2022 Form 2441 Credit Limit Worksheet: cap at tax before credits less
+        # the foreign tax credit (the section 26 cap is unchanged by OBBBA).
+        itaxbc = tax_unit("income_tax_before_credits", period)
+        offset = tax_unit("foreign_tax_credit", period)
+        cap = max_(itaxbc - offset, 0)
+        return min_(cdcc, cap)
diff --git a/policyengine_us/variables/gov/states/ca/tax/income/credits/ca_cdcc_relevant_expenses.py b/policyengine_us/variables/gov/states/ca/tax/income/credits/ca_cdcc_relevant_expenses.py
index 498eec75dbd..25fe3bf1736 100644
--- a/policyengine_us/variables/gov/states/ca/tax/income/credits/ca_cdcc_relevant_expenses.py
+++ b/policyengine_us/variables/gov/states/ca/tax/income/credits/ca_cdcc_relevant_expenses.py
@@ -28,7 +28,15 @@ def formula(tax_unit, period, parameters):
         count_eligible = min_(
             cdcc.eligibility.max, tax_unit("count_cdcc_eligible", period)
         )
-        eligible_capped_expenses = min_(expenses, cdcc.max * count_eligible)
+        # FTB 3506 Part IV (lines 26-33) reduces the $3,000 / $6,000 dollar
+        # limit by the IRC § 129 employer-provided dependent care benefits
+        # excluded from income (line 30 subtracts the excluded benefits, and
+        # line 32 caps at the already-net federal Form 2441 line 31). Mirror the
+        # § 21(c) reduction the federal credit's base applies.
+        dollar_limit = cdcc.max * count_eligible
+        exclusion = tax_unit("dependent_care_assistance_exclusion", period)
+        dollar_limit_after_exclusion = max_(dollar_limit - exclusion, 0)
+        eligible_capped_expenses = min_(expenses, dollar_limit_after_exclusion)
         # Then, cap further to the lowest earnings between the taxpayer and spouse
         return min_(
             eligible_capped_expenses,
diff --git a/policyengine_us/variables/gov/states/id/tax/income/subtractions/household_and_dependent_care/id_cdcc_limit.py b/policyengine_us/variables/gov/states/id/tax/income/subtractions/household_and_dependent_care/id_cdcc_limit.py
index f8b209e8dea..66d8b326980 100644
--- a/policyengine_us/variables/gov/states/id/tax/income/subtractions/household_and_dependent_care/id_cdcc_limit.py
+++ b/policyengine_us/variables/gov/states/id/tax/income/subtractions/household_and_dependent_care/id_cdcc_limit.py
@@ -17,4 +17,9 @@ def formula(tax_unit, period, parameters):
             instant_str = period
         p = parameters(instant_str).gov.irs.credits.cdcc
         capped_count_cdcc_eligible = tax_unit("capped_count_cdcc_eligible", period)
+        # This is the raw federal per-qualifying-individual dollar limit. The
+        # IRC § 129 employer-benefit reduction (Form 39R Line 6 worksheet line 4)
+        # is applied against the operative Idaho cap in
+        # id_household_and_dependent_care_expense_deduction, so it is not
+        # subtracted here.
         return p.max * capped_count_cdcc_eligible
diff --git a/policyengine_us/variables/gov/states/id/tax/income/subtractions/household_and_dependent_care/id_household_and_dependent_care_expense_deduction.py b/policyengine_us/variables/gov/states/id/tax/income/subtractions/household_and_dependent_care/id_household_and_dependent_care_expense_deduction.py
index ffaafd294be..bfe2b957235 100644
--- a/policyengine_us/variables/gov/states/id/tax/income/subtractions/household_and_dependent_care/id_household_and_dependent_care_expense_deduction.py
+++ b/policyengine_us/variables/gov/states/id/tax/income/subtractions/household_and_dependent_care/id_household_and_dependent_care_expense_deduction.py
@@ -21,6 +21,12 @@ def formula(tax_unit, period, parameters):
         expenses = childcare + adult_care
         # In 2023 Idaho implemented an increased cap independent of the number of children
         limit = max_(tax_unit("id_cdcc_limit", period), p.cap)
+        # Form 39R Line 6 worksheet line 4: the operative cap is reduced by the
+        # IRC § 129 employer-provided dependent care benefits ("excluded
+        # benefits from Part III of Form 2441"), mirroring the § 21(c) reduction
+        # the federal credit's base applies.
+        exclusion = tax_unit("dependent_care_assistance_exclusion", period)
+        limit = max_(limit - exclusion, 0)
         eligible_capped_expenses = min_(expenses, limit)
         # cap further to the lowest earnings between the taxpayer and spouse
         return min_(
diff --git a/policyengine_us/variables/gov/states/ky/tax/income/credits/dependent_care_service/ky_cdcc_potential.py b/policyengine_us/variables/gov/states/ky/tax/income/credits/dependent_care_service/ky_cdcc_potential.py
index 3876680f41f..7a7ea11a9d9 100644
--- a/policyengine_us/variables/gov/states/ky/tax/income/credits/dependent_care_service/ky_cdcc_potential.py
+++ b/policyengine_us/variables/gov/states/ky/tax/income/credits/dependent_care_service/ky_cdcc_potential.py
@@ -11,8 +11,16 @@ class ky_cdcc_potential(Variable):
     defined_for = StateCode.KY
 
     def formula(tax_unit, period, parameters):
-        # Kentucky matches the federal credit taken
-        dependent_care_credit = tax_unit("cdcc", period)
+        # Kentucky matches the federal credit taken. KRS 141.067 sets the credit
+        # at 20% of "the federal credit allowed under Section 21 of the Internal
+        # Revenue Code," and KRS 141.010(21) fixes Kentucky's IRC at the Code in
+        # effect on December 31, 2024. From 2026 that frozen Code excludes the
+        # OBBBA section 21 rate increase (effective for tax years beginning after
+        # 2025-12-31), so Kentucky uses the pre-OBBBA federal credit.
+        if period.start.year >= 2026:
+            dependent_care_credit = tax_unit("pre_obbba_cdcc", period)
+        else:
+            dependent_care_credit = tax_unit("cdcc", period)
         rate = parameters(
             period
         ).gov.states.ky.tax.income.credits.dependent_care_service.match
diff --git a/policyengine_us/variables/gov/states/me/tax/income/credits/child_care_credit/me_child_care_credit.py b/policyengine_us/variables/gov/states/me/tax/income/credits/child_care_credit/me_child_care_credit.py
index f9b79a4fe12..41dd4dfb512 100644
--- a/policyengine_us/variables/gov/states/me/tax/income/credits/child_care_credit/me_child_care_credit.py
+++ b/policyengine_us/variables/gov/states/me/tax/income/credits/child_care_credit/me_child_care_credit.py
@@ -21,8 +21,16 @@ def formula(tax_unit, period, parameters):
             "me_step_4_share_of_child_care_expenses", period
         )
         # Line 2: Divide Federal CDCC according to share of regular vs. Step 4 expenses
-        # Maine matches the federal credit taken
-        cdcc = tax_unit("cdcc", period)
+        # Maine matches the federal credit taken. 36 M.R.S. § 5218 sets the
+        # credit at 25% of "the federal tax credit allowable for child and
+        # dependent care expenses," and 36 M.R.S. § 111(1-A) fixes Maine's
+        # "Code" at the IRC and amendments as of December 31, 2024. From 2026
+        # that frozen Code excludes the OBBBA section 21 rate increase, so Maine
+        # uses the pre-OBBBA federal credit.
+        if period.start.year >= 2026:
+            cdcc = tax_unit("pre_obbba_cdcc", period)
+        else:
+            cdcc = tax_unit("cdcc", period)
         # Line 2a: Column A
         cdcc_regular_portion = cdcc * (1 - step_4_share_of_expenses)
         # Line 2a, Column B
diff --git a/policyengine_us/variables/gov/states/sc/tax/income/credits/cdcc/sc_cdcc_potential.py b/policyengine_us/variables/gov/states/sc/tax/income/credits/cdcc/sc_cdcc_potential.py
index 3b913d3107b..beece662287 100644
--- a/policyengine_us/variables/gov/states/sc/tax/income/credits/cdcc/sc_cdcc_potential.py
+++ b/policyengine_us/variables/gov/states/sc/tax/income/credits/cdcc/sc_cdcc_potential.py
@@ -8,7 +8,10 @@ class sc_cdcc_potential(Variable):
     documentation = "South Carolina Child and Dependent Care Credit"
     unit = USD
     definition_period = YEAR
-    reference = "https://dor.sc.gov/forms-site/Forms/IITPacket_2022.pdf#page=22"
+    reference = (
+        "https://www.scstatehouse.gov/code/t12c006.php",  # S.C. Code § 12-6-3380
+        "https://dor.sc.gov/forms-site/Forms/IITPacket_2022.pdf#page=22",
+    )
     defined_for = StateCode.SC
 
     def formula(tax_unit, period, parameters):
@@ -24,9 +27,16 @@ def formula(tax_unit, period, parameters):
         # Get child care expenses.
         childcare_expenses = tax_unit("cdcc_relevant_expenses", period)
 
-        # Married filing separate are ineligible.
-        filing_status = tax_unit("filing_status", period)
-        eligible = filing_status != filing_status.possible_values.SEPARATE
+        # S.C. Code Ann. § 12-6-3380 computes the credit "as provided in
+        # Internal Revenue Code Section 21," importing § 21 wholesale with only
+        # the applicable-percentage (7%) and SC-source-income modifications. It
+        # adds no filing-status language of its own, so it carries the
+        # § 21(e)(2) joint-return requirement together with the § 21(e)(4)
+        # separated-taxpayer exception. A married-separate filer who lives apart
+        # while maintaining a home for a qualifying individual is therefore
+        # eligible, matching the federal treatment; an ordinary MFS filer
+        # remains ineligible.
+        eligible = tax_unit("cdcc_filing_status_eligible", period)
 
         # Number of qualifying people
         count_cdcc_eligible = min_(
diff --git a/policyengine_us/variables/gov/states/va/tax/income/deductions/cdcc_expense/va_child_dependent_care_deduction_cdcc_limit.py b/policyengine_us/variables/gov/states/va/tax/income/deductions/cdcc_expense/va_child_dependent_care_deduction_cdcc_limit.py
index 249f824ece5..0b9f8324eb9 100644
--- a/policyengine_us/variables/gov/states/va/tax/income/deductions/cdcc_expense/va_child_dependent_care_deduction_cdcc_limit.py
+++ b/policyengine_us/variables/gov/states/va/tax/income/deductions/cdcc_expense/va_child_dependent_care_deduction_cdcc_limit.py
@@ -17,4 +17,12 @@ def formula(tax_unit, period, parameters):
             instant_str = period
         p = parameters(instant_str).gov.irs.credits.cdcc
         capped_count_cdcc_eligible = tax_unit("capped_count_cdcc_eligible", period)
-        return p.max * capped_count_cdcc_eligible
+        dollar_limit = p.max * capped_count_cdcc_eligible
+        # Va. Code § 58.1-322.03(3) deducts "the amount of employment-related
+        # expenses upon which the federal credit is based under § 21," and the
+        # Form 760 code 101 instruction points to the Form 2441 amount that is
+        # multiplied by the decimal (line 31) — already reduced by the IRC § 129
+        # employer-provided dependent care benefits under § 21(c). Mirror that
+        # reduction so the deduction base matches the federal credit's base.
+        exclusion = tax_unit("dependent_care_assistance_exclusion", period)
+        return max_(dollar_limit - exclusion, 0)
diff --git a/policyengine_us/variables/gov/states/vt/tax/income/credits/cdcc/vt_cdcc.py b/policyengine_us/variables/gov/states/vt/tax/income/credits/cdcc/vt_cdcc.py
index aa0e966e853..6b613164326 100644
--- a/policyengine_us/variables/gov/states/vt/tax/income/credits/cdcc/vt_cdcc.py
+++ b/policyengine_us/variables/gov/states/vt/tax/income/credits/cdcc/vt_cdcc.py
@@ -17,8 +17,16 @@ class vt_cdcc(Variable):
 
     def formula(tax_unit, period, parameters):
         p = parameters(period).gov.states.vt.tax.income.credits.cdcc
-        # The form refers to 2022 Form 2441 line 11, which caps the credit at tax liability.
-        federal_cdcc = tax_unit("capped_cdcc", period)
+        # The form refers to 2022 Form 2441 line 11, which caps the credit at tax
+        # liability. 32 V.S.A. § 5828c sets the credit at 72% of "the federal
+        # child and dependent care credit allowed to the taxpayer," and § 5824
+        # adopts the federal income tax laws as in effect on December 31, 2024.
+        # From 2026 that frozen Code excludes the OBBBA section 21 rate increase,
+        # so Vermont uses the pre-OBBBA federal credit.
+        if period.start.year >= 2026:
+            federal_cdcc = tax_unit("pre_obbba_capped_cdcc", period)
+        else:
+            federal_cdcc = tax_unit("capped_cdcc", period)
         # 2022 Act 138 raised the 5828c match to 72 percent but retained the
         # low-income adjusted gross income cap and the certified-facility
         # requirement for 2022; 2023 Act 72 removed them effective 2023. We
diff --git a/policyengine_us/variables/gov/states/vt/tax/income/credits/cdcc/vt_low_income_cdcc.py b/policyengine_us/variables/gov/states/vt/tax/income/credits/cdcc/vt_low_income_cdcc.py
index c02a3365d83..2ee5fc89db3 100644
--- a/policyengine_us/variables/gov/states/vt/tax/income/credits/cdcc/vt_low_income_cdcc.py
+++ b/policyengine_us/variables/gov/states/vt/tax/income/credits/cdcc/vt_low_income_cdcc.py
@@ -15,5 +15,11 @@ class vt_low_income_cdcc(Variable):
 
     def formula(tax_unit, period, parameters):
         p = parameters(period).gov.states.vt.tax.income.credits.cdcc.low_income
-        federal_cdcc = tax_unit("capped_cdcc", period)
+        # 32 V.S.A. § 5824 adopts the federal income tax laws as in effect on
+        # December 31, 2024, so from 2026 Vermont uses the pre-OBBBA federal
+        # credit (excluding the OBBBA section 21 rate increase).
+        if period.start.year >= 2026:
+            federal_cdcc = tax_unit("pre_obbba_capped_cdcc", period)
+        else:
+            federal_cdcc = tax_unit("capped_cdcc", period)
         return p.rate * federal_cdcc