format fixes

changelog_entry.yaml

@@ -1,4 +1,4 @@
 - bump: minor
   changes:
     added:
-    - Reafctor the Alternative Minimum Tax (AMT) logic.
+    - Refactor the Alternative Minimum Tax (AMT) logic.

policyengine_us/parameters/gov/irs/income/amt/multiplier.yaml

@@ -0,0 +1,21 @@
+description: The IRS multiplies the Alternative Minimum Tax income tax brackets by this rate, based on filing status.
+metadata:
+  unit: /1
+  period: year
+  breakdown:
+    - filing_status
+  label: AMT tax bracket multiplier
+  reference:
+    - title: 26 U.S. Code § 55 - Alternative minimum tax imposed (b)(1)(C)
+      href: https://www.law.cornell.edu/uscode/text/26/55#b_1_C
+
+SINGLE:
+  2013-01-01: 1
+JOINT:
+  2013-01-01: 1
+HEAD_OF_HOUSEHOLD:
+  2013-01-01: 1
+SURVIVING_SPOUSE:
+  2013-01-01: 0.5
+SEPARATE:
+  2013-01-01: 1

policyengine_us/tests/policy/baseline/gov/irs/tax/federal_income/alternative_minimum_tax/base_tax/amt_higher_base_tax.yaml

@@ -0,0 +1,23 @@
+- name: Single person, low income
+  period: 2022
+  input:
+    filing_status: SINGLE
+    amt_income_less_exemptions: 10_000
+  output:
+    amt_higher_base_tax: 0
+
+- name: Single person, 400k income
+  period: 2022
+  input:
+    filing_status: SINGLE
+    amt_income_less_exemptions: 400_000
+  output:
+    amt_higher_base_tax: 54_292
+
+- name: Joint, 600k income
+  period: 2022
+  input:
+    filing_status: JOINT
+    amt_income_less_exemptions: 600_000
+  output:
+    amt_higher_base_tax: 110_292

policyengine_us/tests/policy/baseline/gov/irs/tax/federal_income/alternative_minimum_tax/base_tax/amt_lower_base_tax.yaml

@@ -0,0 +1,23 @@
+- name: Single person, low income
+  period: 2022
+  input:
+    filing_status: SINGLE
+    amt_income_less_exemptions: 10_000
+  output:
+    amt_lower_base_tax: 2_600
+
+- name: Single person, no income
+  period: 2022
+  input:
+    filing_status: SINGLE
+    amt_income_less_exemptions: 0
+  output:
+    amt_lower_base_tax: 0
+
+- name: Joint, high income
+  period: 2022
+  input:
+    filing_status: JOINT
+    amt_income_less_exemptions: 400_000
+  output:
+    amt_lower_base_tax: 53_586

policyengine_us/variables/gov/irs/tax/federal_income/alternative_minimum_tax/base_tax/amt_base_tax.py

@@ -0,0 +1,16 @@
+from policyengine_us.model_api import *
+
+
+class amt_base_tax(Variable):
+    value_type = float
+    entity = TaxUnit
+    definition_period = YEAR
+    label = "Alternative Minimum Tax base tax"
+    unit = USD
+    documentation = "Alternative Minimum Tax (AMT) base tax, Form 6251 Part II Line 7 'All Others'"
+    reference = "https://www.irs.gov/pub/irs-pdf/f6251.pdf"
+
+    adds = [
+        "amt_lower_base_tax",
+        "amt_higher_base_tax",
+    ]

policyengine_us/variables/gov/irs/tax/federal_income/alternative_minimum_tax/amt_base_tax.py → policyengine_us/variables/gov/irs/tax/federal_income/alternative_minimum_tax/base_tax/amt_higher_base_tax.py

@@ -1,27 +1,20 @@
 from policyengine_us.model_api import *
 
 
-class amt_base_tax(Variable):
+class amt_higher_base_tax(Variable):
     value_type = float
     entity = TaxUnit
     definition_period = YEAR
-    label = "Alternative Minimum Tax"
+    label = "Alternative Minimum Tax higher base tax amount"
     unit = USD
-    documentation = "Alternative Minimum Tax (AMT) base tax, Form 6251 Part II Line 7 'All Others'"
+    documentation = "Alternative Minimum Tax (AMT) base tax, Form 6251 Part II Line 7 'All Others' - higher bracket"
     reference = "https://www.irs.gov/pub/irs-pdf/f6251.pdf"
 
     def formula(tax_unit, period, parameters):
         p = parameters(period).gov.irs.income.amt
         filing_status = tax_unit("filing_status", period)
         reduced_income = tax_unit("amt_income_less_exemptions", period)
-        bracket_fraction = where(
-            filing_status == filing_status.possible_values.SEPARATE,
-            0.5,
-            1.0,
-        )
+        bracket_fraction = p.multiplier[filing_status]
         tax_rate_threshold = p.brackets.thresholds[-1] * bracket_fraction
-        lower_rate = p.brackets.rates[0]
         higher_rate = p.brackets.rates[1]
-        lower_tax = min_(reduced_income, tax_rate_threshold) * lower_rate
-        higher_tax = max_(0, reduced_income - tax_rate_threshold) * higher_rate
-        return lower_tax + higher_tax
+        return max_(0, reduced_income - tax_rate_threshold) * higher_rate

policyengine_us/variables/gov/irs/tax/federal_income/alternative_minimum_tax/base_tax/amt_lower_base_tax.py

@@ -0,0 +1,20 @@
+from policyengine_us.model_api import *
+
+
+class amt_lower_base_tax(Variable):
+    value_type = float
+    entity = TaxUnit
+    definition_period = YEAR
+    label = "Alternative Minimum Tax lower base tax amount"
+    unit = USD
+    documentation = "Alternative Minimum Tax (AMT) base tax, Form 6251 Part II Line 7 'All Others' - lower bracket"
+    reference = "https://www.irs.gov/pub/irs-pdf/f6251.pdf"
+
+    def formula(tax_unit, period, parameters):
+        p = parameters(period).gov.irs.income.amt
+        filing_status = tax_unit("filing_status", period)
+        reduced_income = tax_unit("amt_income_less_exemptions", period)
+        bracket_fraction = p.multiplier[filing_status]
+        tax_rate_threshold = p.brackets.thresholds[-1] * bracket_fraction
+        lower_rate = p.brackets.rates[0]
+        return min_(reduced_income, tax_rate_threshold) * lower_rate

policyengine_us/variables/gov/irs/tax/federal_income/alternative_minimum_tax/kiddie_tax/amt_kiddie_tax_applies.py

@@ -10,7 +10,7 @@ class amt_kiddie_tax_applies(Variable):
 
     def formula(tax_unit, period, parameters):
         age_head = tax_unit("age_head", period)
-        child = parameters(period).gov.irs.dependent.ineligible_age
-        young_head = (age_head != 0) & (age_head < child.non_student)
-        no_or_young_spouse = tax_unit("age_spouse", period) < child.non_student
+        p = parameters(period).gov.irs.dependent.ineligible_age
+        young_head = (age_head != 0) & (age_head < p.non_student)
+        no_or_young_spouse = tax_unit("age_spouse", period) < p.non_student
         return young_head & no_or_young_spouse