Remove the Montana CTC for the enacted policies (#5578)

* Remove the Montana CTC for the enacted policies
Fixes #5577

* minor

* remove from state ctcs

changelog_entry.yaml

@@ -0,0 +1,4 @@
+- bump: patch
+  changes:
+    fixes:
+    - Convert the Montana Child Tax Credit to a reform.

policyengine_us/parameters/gov/states/mt/tax/income/credits/ctc/amount.yaml → policyengine_us/parameters/gov/contrib/states/mt/ctc/amount.yaml

@@ -16,8 +16,6 @@ metadata:
   period: year
   label: Montana child tax credit base
   reference:
-  # The Montana Child Tax Credit established in the 2023 House Bill No. 268
-  # not existent before
     - title: 2023 Montana Legislature, House Bill No. 268, Section 1.(2) & Section 1.(7)-(c)
       href: https://leg.mt.gov/bills/2023/billhtml/HB0268.htm
 

policyengine_us/parameters/gov/contrib/states/mt/ctc/in_effect.yaml

@@ -0,0 +1,13 @@
+description: The Montana Child Tax Credit is in effect if this is true.
+
+values:
+  0000-01-01: false
+
+metadata:
+  unit: bool
+  period: year
+  label: Montana Child Tax Credit in effect
+  reference:
+    - title: 2023 Montana Legislature, House Bill No. 268, Section 1.(2) & Section 1.(7)-(c)
+      href: https://leg.mt.gov/bills/2023/billhtml/HB0268.htm
+

policyengine_us/parameters/gov/states/mt/tax/income/credits/ctc/reduction/amount.yaml → policyengine_us/parameters/gov/contrib/states/mt/ctc/reduction/amount.yaml

@@ -6,7 +6,5 @@ metadata:
   period: year
   label: Montana child tax credit reduction amount
   reference:
-  # The Montana Child Tax Credit established in the 2023 House Bill No. 268
-  # not existent before
     - title: 2023 Montana Legislature, House Bill No. 268, Section 1-(6)
       href: https://leg.mt.gov/bills/2023/billhtml/HB0268.htm

policyengine_us/parameters/gov/states/mt/tax/income/credits/refundable.yaml

@@ -6,11 +6,7 @@ metadata:
   reference: 
     - title: Montana 2022 Form2 Individual Income Tax Instructions
       href: https://mtrevenue.gov/wp-content/uploads/dlm_uploads/2022/12/Form-2-2022-Instructions.pdf#page=17
-    - title: 2023 Montana Legislature, House Bill No. 268, Section 1
-      href: https://leg.mt.gov/bills/2023/billhtml/HB0268.htm
+
 values:
   2021-01-01:
     - mt_eitc
-  2023-01-01:
-    - mt_ctc
-    - mt_eitc

policyengine_us/reforms/reforms.py

@@ -86,6 +86,10 @@
     create_nyc_school_tax_credit_with_phase_out_reform,
 )
 
+from .states.mt.ctc import (
+    create_mt_ctc_reform,
+)
+
 from policyengine_core.reforms import Reform
 import warnings
 
@@ -188,6 +192,7 @@ def create_structural_reforms_from_parameters(parameters, period):
     nyc_school_tax_credit_with_phase_out = (
         create_nyc_school_tax_credit_with_phase_out_reform(parameters, period)
     )
+    mt_ctc = create_mt_ctc_reform(parameters, period)
 
     reforms = [
         afa_reform,
@@ -226,6 +231,7 @@ def create_structural_reforms_from_parameters(parameters, period):
         ny_2025_inflation_rebates,
         limit_salt_deduction_to_property_taxes,
         nyc_school_tax_credit_with_phase_out,
+        mt_ctc,
     ]
     reforms = tuple(filter(lambda x: x is not None, reforms))
 

policyengine_us/reforms/states/mt/ctc/__init__.py

@@ -0,0 +1,3 @@
+from .mt_ctc import (
+    create_mt_ctc_reform,
+)

policyengine_us/reforms/states/mt/ctc/mt_ctc.py

@@ -0,0 +1,93 @@
+from policyengine_us.model_api import *
+from policyengine_core.periods import period as period_
+from policyengine_core.periods import instant
+
+
+def create_mt_ctc() -> Reform:
+    class mt_ctc(Variable):
+        value_type = float
+        entity = TaxUnit
+        label = "Montana Child Tax Credit"
+        definition_period = YEAR
+        unit = USD
+        reference = "https://leg.mt.gov/bills/2023/billpdf/HB0268.pdf"
+        defined_for = "mt_ctc_eligible"
+
+        def formula(tax_unit, period, parameters):
+            p = parameters(period).gov.contrib.states.mt.ctc
+            person = tax_unit.members
+            age = person("age", period)
+            credit_amount = tax_unit.sum(p.amount.calc(age))
+            # Credit gets reduced by an amount for each increment that AGI exceeds a certain threshold
+            agi = tax_unit("adjusted_gross_income", period)
+            excess = max_(agi - p.reduction.threshold, 0)
+            increments = excess // p.reduction.increment
+            reduction = p.reduction.amount * increments
+            return max_(credit_amount - reduction, 0)
+
+    class mt_ctc_eligible(Variable):
+        value_type = bool
+        entity = TaxUnit
+        label = "Eligible for the Montana Child Tax Credit"
+        definition_period = YEAR
+        reference = "https://leg.mt.gov/bills/2023/billpdf/HB0268.pdf"
+        defined_for = StateCode.MT
+
+        def formula(tax_unit, period, parameters):
+            p = parameters(period).gov.contrib.states.mt.ctc.income_limit
+            agi = tax_unit("adjusted_gross_income", period)
+            agi_eligible = agi <= p.agi
+            # CTC limited to filers with investment income below a certain threshold
+            investment_income_eligible = (
+                tax_unit("eitc_relevant_investment_income", period)
+                < p.investment
+            )
+
+            earned_income = tax_unit("tax_unit_earned_income", period)
+            receives_earned_income = earned_income > 0
+
+            return (
+                agi_eligible
+                & investment_income_eligible
+                & receives_earned_income
+            )
+
+    def modify_parameters(parameters):
+        parameters.gov.states.mt.tax.income.credits.refundable.update(
+            start=instant("2023-01-01"),
+            stop=instant("2031-12-31"),
+            value=["mt_ctc", "mt_eitc"],
+        )
+        return parameters
+
+    class reform(Reform):
+        def apply(self):
+            self.update_variable(mt_ctc)
+            self.update_variable(mt_ctc_eligible)
+            self.modify_parameters(modify_parameters)
+
+    return reform
+
+
+def create_mt_ctc_reform(parameters, period, bypass: bool = False):
+    if bypass:
+        return create_mt_ctc()
+
+    p = parameters.gov.contrib.states.mt.ctc
+
+    reform_active = False
+    current_period = period_(period)
+
+    for i in range(5):
+        if p(current_period).in_effect:
+            reform_active = True
+            break
+        current_period = current_period.offset(1, "year")
+
+    if reform_active:
+        return create_mt_ctc()
+    else:
+        return None
+
+
+mt_ctc = create_mt_ctc_reform(None, None, bypass=True)