South Carolina Net Capital Gain Deduction

changelog_entry.yaml

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+- bump: minor
+  changes:
+    added:
+    - South Carolina net capital gain deduction.

policyengine_us/parameters/gov/states/sc/tax/income/deductions/net_capital_gain_deduction/rate.yaml

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+description: South Carolina deducts this fraction of net capital gains from taxable income. 
+values: 
+  2021-01-01: 0.44
+
+metadata:
+  unit: /1
+  period: year
+  label: South Carolina net capital gain deduction rate
+  reference:
+  - title: SC1040 tax form (2021)
+    href: https://dor.sc.gov/forms-site/Forms/SC1040_2021.pdf#page=2
+  - title: Instructions for Form SC-1040 (line 3i)
+    href: https://dor.sc.gov/forms-site/Forms/IITPacket_2021.pdf#page=15
+  - title: South Carolina Code of Laws Section 12-6-1150 (A)
+    href: https://www.scstatehouse.gov/code/t12c006.php
+  - title: SC1040 tax form (2022)
+    href: https://dor.sc.gov/forms-site/Forms/SC1040_2022.pdf#page=2

policyengine_us/tests/policy/baseline/gov/states/sc/tax/income/deductions/net_captial_gain_deduction/sc_net_capital_gain_deduction.yaml

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+- name: Case 1, capital_gains is positive
+  period: 2021
+  input:
+    state_code: SC
+    net_capital_gain: 1_000
+  output: 
+    sc_net_capital_gain_deduction: 440

policyengine_us/variables/gov/states/sc/tax/income/deductions/net_capital_gain_deduction/sc_net_capital_gain_deduction.py

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+from policyengine_us.model_api import *
+
+
+class sc_net_capital_gain_deduction(Variable):
+    value_type = float
+    entity = TaxUnit
+    label = "South Carolina net capital gain deduction"
+    unit = USD
+    definition_period = YEAR
+    defined_for = StateCode.SC
+    reference = (
+        "https://dor.sc.gov/forms-site/Forms/IITPacket_2021.pdf#page=15",
+        "https://www.scstatehouse.gov/code/t12c006.php"
+        # South Carolina Code of Laws Section 12-6-1150 (A)
+    )
+
+    def formula(tax_unit, period, parameters):
+        p = parameters(
+            period
+        ).gov.states.sc.tax.income.deductions.net_capital_gain_deduction
+        capital_gains = tax_unit("net_capital_gain", period)
+        return capital_gains * p.rate