Add South Carolina homestead property tax exemption

changelog.d/8311.added.md

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+Added the South Carolina Homestead Exemption property tax reduction.

policyengine_us/parameters/gov/states/sc/tax/property/homestead_exemption/age_threshold.yaml

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+description: South Carolina limits age-based eligibility to this threshold under the Homestead Exemption program.
+values:
+  2025-01-01: 65
+metadata:
+  unit: year
+  period: year
+  label: South Carolina homestead exemption age threshold
+  reference:
+    - title: South Carolina Department of Revenue | Exempt Property
+      href: https://dor.sc.gov/property/exempt-property
+    - title: South Carolina Code Section 12-37-250
+      href: https://www.scstatehouse.gov/code/t12c037.php

policyengine_us/parameters/gov/states/sc/tax/property/homestead_exemption/amount.yaml

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+description: South Carolina provides this fair market value exemption amount under the Homestead Exemption program.
+values:
+  2025-01-01: 50_000
+metadata:
+  unit: currency-USD
+  period: year
+  label: South Carolina homestead exemption amount
+  reference:
+    - title: South Carolina Department of Revenue | Exempt Property
+      href: https://dor.sc.gov/property/exempt-property
+    - title: South Carolina Code Section 12-37-250
+      href: https://www.scstatehouse.gov/code/t12c037.php

policyengine_us/parameters/gov/states/sc/tax/property/homestead_exemption/assessment_rate.yaml

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+description: South Carolina uses this share of fair market value as assessed value under the Homestead Exemption program.
+values:
+  2025-01-01: 0.04
+metadata:
+  unit: /1
+  period: year
+  label: South Carolina homestead exemption legal residence assessment rate
+  reference:
+    - title: South Carolina Department of Revenue | Exempt Property
+      href: https://dor.sc.gov/property/exempt-property
+    - title: South Carolina Code Section 12-37-252
+      href: https://www.scstatehouse.gov/code/t12c037.php

policyengine_us/tests/policy/baseline/gov/states/sc/tax/property/homestead_exemption/sc_homestead_exemption.yaml

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+- name: Case 1, exemption is capped at the statutory amount.
+  period: 2025
+  input:
+    people:
+      person1:
+        age: 65
+        assessed_property_value: 8_000
+    tax_units:
+      tax_unit:
+        members: [person1]
+    households:
+      household:
+        members: [person1]
+        state_code: SC
+  output:
+    sc_homestead_exemption: 2_000
+
+- name: Case 2, exemption is limited to assessed property value.
+  period: 2025
+  input:
+    people:
+      person1:
+        age: 65
+        assessed_property_value: 1_600
+    tax_units:
+      tax_unit:
+        members: [person1]
+    households:
+      household:
+        members: [person1]
+        state_code: SC
+  output:
+    sc_homestead_exemption: 1_600
+
+- name: Case 3, exemption excludes non-joint adult property value.
+  period: 2025
+  input:
+    people:
+      person1:
+        age: 65
+        assessed_property_value: 1_600
+      person2:
+        age: 40
+        assessed_property_value: 8_000
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+        filing_status: SINGLE
+    households:
+      household:
+        members: [person1, person2]
+        state_code: SC
+  output:
+    sc_homestead_exemption: 1_600

policyengine_us/tests/policy/baseline/gov/states/sc/tax/property/homestead_exemption/sc_homestead_exemption_eligible.yaml

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+- name: Case 1, senior homeowner is eligible.
+  period: 2025
+  input:
+    people:
+      person1:
+        age: 65
+        assessed_property_value: 8_000
+    tax_units:
+      tax_unit:
+        members: [person1]
+    households:
+      household:
+        members: [person1]
+        state_code: SC
+  output:
+    sc_homestead_exemption_eligible: true
+
+- name: Case 2, disabled homeowner under age 65 is eligible.
+  period: 2025
+  input:
+    people:
+      person1:
+        age: 40
+        is_disabled: true
+        assessed_property_value: 8_000
+    tax_units:
+      tax_unit:
+        members: [person1]
+    households:
+      household:
+        members: [person1]
+        state_code: SC
+  output:
+    sc_homestead_exemption_eligible: true
+
+- name: Case 3, blind homeowner under age 65 is eligible.
+  period: 2025
+  input:
+    people:
+      person1:
+        age: 40
+        is_blind: true
+        assessed_property_value: 8_000
+    tax_units:
+      tax_unit:
+        members: [person1]
+    households:
+      household:
+        members: [person1]
+        state_code: SC
+  output:
+    sc_homestead_exemption_eligible: true
+
+- name: Case 4, non-senior homeowner without disability or blindness is ineligible.
+  period: 2025
+  input:
+    people:
+      person1:
+        age: 64
+        assessed_property_value: 8_000
+    tax_units:
+      tax_unit:
+        members: [person1]
+    households:
+      household:
+        members: [person1]
+        state_code: SC
+  output:
+    sc_homestead_exemption_eligible: false
+
+- name: Case 5, senior without assessed property is ineligible.
+  period: 2025
+  input:
+    people:
+      person1:
+        age: 65
+    tax_units:
+      tax_unit:
+        members: [person1]
+    households:
+      household:
+        members: [person1]
+        state_code: SC
+  output:
+    sc_homestead_exemption_eligible: false
+
+- name: Case 6, joint spouse meeting the age test is eligible.
+  period: 2025
+  input:
+    people:
+      person1:
+        age: 40
+        assessed_property_value: 8_000
+        is_tax_unit_head: true
+      person2:
+        age: 65
+        is_tax_unit_spouse: true
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+        filing_status: JOINT
+    households:
+      household:
+        members: [person1, person2]
+        state_code: SC
+  output:
+    sc_homestead_exemption_eligible: true
+
+- name: Case 7, non-joint adult meeting the age test is ineligible.
+  period: 2025
+  input:
+    people:
+      person1:
+        age: 40
+        assessed_property_value: 8_000
+        is_tax_unit_head: true
+      person2:
+        age: 65
+        is_tax_unit_spouse: true
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+        filing_status: SINGLE
+    households:
+      household:
+        members: [person1, person2]
+        state_code: SC
+  output:
+    sc_homestead_exemption_eligible: false

policyengine_us/tests/policy/baseline/gov/states/sc/tax/property/homestead_exemption/sc_homestead_property_tax_reduction.yaml

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+- name: Case 1, reduction equals the property tax on the exempt share of value.
+  period: 2025
+  input:
+    people:
+      person1:
+        age: 65
+        assessed_property_value: 8_000
+        real_estate_taxes: 2_000
+    tax_units:
+      tax_unit:
+        members: [person1]
+    households:
+      household:
+        members: [person1]
+        state_code: SC
+  output:
+    sc_homestead_property_tax_reduction: 500
+
+- name: Case 2, reduction cannot exceed property taxes.
+  period: 2025
+  input:
+    people:
+      person1:
+        age: 65
+        assessed_property_value: 1_600
+        real_estate_taxes: 800
+    tax_units:
+      tax_unit:
+        members: [person1]
+    households:
+      household:
+        members: [person1]
+        state_code: SC
+  output:
+    sc_homestead_property_tax_reduction: 800
+
+- name: Case 3, ineligible filer gets no reduction.
+  period: 2025
+  input:
+    people:
+      person1:
+        age: 64
+        assessed_property_value: 8_000
+        real_estate_taxes: 2_000
+    tax_units:
+      tax_unit:
+        members: [person1]
+    households:
+      household:
+        members: [person1]
+        state_code: SC
+  output:
+    sc_homestead_property_tax_reduction: 0
+
+- name: Case 4, reduction excludes non-joint adult property tax.
+  period: 2025
+  input:
+    people:
+      person1:
+        age: 65
+        assessed_property_value: 1_600
+        real_estate_taxes: 800
+      person2:
+        age: 40
+        assessed_property_value: 8_000
+        real_estate_taxes: 2_000
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+        filing_status: SINGLE
+    households:
+      household:
+        members: [person1, person2]
+        state_code: SC
+  output:
+    sc_homestead_property_tax_reduction: 800

policyengine_us/variables/gov/states/sc/tax/property/homestead_exemption/sc_homestead_exemption.py

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+from policyengine_us.model_api import *
+
+
+class sc_homestead_exemption(Variable):
+    value_type = float
+    entity = TaxUnit
+    label = "South Carolina homestead exemption"
+    unit = USD
+    definition_period = YEAR
+    reference = "https://dor.sc.gov/property/exempt-property"
+    defined_for = "sc_homestead_exemption_eligible"
+
+    def formula(tax_unit, period, parameters):
+        p = parameters(period).gov.states.sc.tax.property.homestead_exemption
+        person = tax_unit.members
+        head = person("is_tax_unit_head", period)
+        joint_spouse = person("is_tax_unit_spouse", period) & person.tax_unit(
+            "tax_unit_is_joint", period
+        )
+        assessed_value = tax_unit.sum(
+            person("assessed_property_value", period) * (head | joint_spouse)
+        )
+        assessed_exemption_amount = p.amount * p.assessment_rate
+        return min_(
+            assessed_value,
+            assessed_exemption_amount,
+        )

policyengine_us/variables/gov/states/sc/tax/property/homestead_exemption/sc_homestead_exemption_eligible.py

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+from policyengine_us.model_api import *
+
+
+class sc_homestead_exemption_eligible(Variable):
+    value_type = bool
+    entity = TaxUnit
+    label = "Eligible for the South Carolina Homestead Exemption"
+    definition_period = YEAR
+    reference = "https://dor.sc.gov/property/exempt-property"
+    defined_for = StateCode.SC
+
+    def formula(tax_unit, period, parameters):
+        p = parameters(period).gov.states.sc.tax.property.homestead_exemption
+        person = tax_unit.members
+        head = person("is_tax_unit_head", period)
+        joint_spouse = person("is_tax_unit_spouse", period) & person.tax_unit(
+            "tax_unit_is_joint", period
+        )
+        head_or_joint_spouse = head | joint_spouse
+        age = person("age", period.this_year)
+        is_disabled = person("is_disabled", period)
+        is_blind = person("is_blind", period)
+        assessed_value = person("assessed_property_value", period)
+
+        return tax_unit.any(
+            ((age >= p.age_threshold) | is_disabled | is_blind) & head_or_joint_spouse,
+        ) & (tax_unit.sum(assessed_value * head_or_joint_spouse) > 0)

policyengine_us/variables/gov/states/sc/tax/property/homestead_exemption/sc_homestead_property_tax_reduction.py

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+from policyengine_us.model_api import *
+
+
+class sc_homestead_property_tax_reduction(Variable):
+    value_type = float
+    entity = TaxUnit
+    label = "South Carolina homestead property tax reduction"
+    unit = USD
+    definition_period = YEAR
+    reference = "https://dor.sc.gov/property/exempt-property"
+    defined_for = "sc_homestead_exemption_eligible"
+
+    def formula(tax_unit, period, parameters):
+        person = tax_unit.members
+        head = person("is_tax_unit_head", period)
+        joint_spouse = person("is_tax_unit_spouse", period) & person.tax_unit(
+            "tax_unit_is_joint", period
+        )
+        head_or_joint_spouse = head | joint_spouse
+        assessed_value = tax_unit.sum(
+            person("assessed_property_value", period) * head_or_joint_spouse
+        )
+        real_estate_taxes = tax_unit.sum(
+            person("real_estate_taxes", period) * head_or_joint_spouse
+        )
+
+        return real_estate_taxes * (
+            tax_unit("sc_homestead_exemption", period) / max_(assessed_value, 1)
+        )