Added Montana Interest Exemptions (#3098)

* Added Montana Interest Exemptions
Fixes #3058

* Adjusted

* Revised

* Revised

* Revised

* Add subtractions

* Revised

* Revised

* Revised

* revised

* Revised

* Update policyengine_us/parameters/gov/states/mt/tax/income/exemptions/interest/cap.yaml

* Update policyengine_us/variables/gov/states/mt/tax/income/exemptions/mt_interest_exemption_eligible.py

---------

Co-authored-by: Pavel Makarchuk <[email protected]>

changelog_entry.yaml

@@ -0,0 +1,4 @@
+- bump: minor
+  changes:
+    added:
+    - Montana senior interest income exclusion.

policyengine_us/parameters/gov/states/mt/tax/income/exemptions/amount.yaml

@@ -13,3 +13,4 @@ metadata:
   unit: currency-USD
   period: year
   label: Montana income tax exemption amount
+

policyengine_us/parameters/gov/states/mt/tax/income/exemptions/interest/age_threshold.yaml

@@ -0,0 +1,14 @@
+description: Montana partially excludes interest from adjusted gross income of filers and spouses at or above this age threshold. 
+metadata:
+  label: Montana senior interest income exclusion age threshold
+  period: year
+  unit: year
+  reference:
+    - title: 2021 Montana Form 2 | line 3 - Partial Interest Exemption for Taxpayers
+      href: https://mtrevenue.gov/wp-content/uploads/mdocs/form%202%202021%20instructions.pdf#page=24
+    - title: 2022 Montana Form 2 | line 3 - Partial Interest Exemption for Taxpayers
+      href: https://mtrevenue.gov/wp-content/uploads/dlm_uploads/2022/12/Form-2-2022-Instructions.pdf#page=25
+    - title: Administrative Rules of Montana | Income Taxes | § 42.14.215 (4)
+      href: https://rules.mt.gov/gateway/RuleNo.asp?RN=42%2E15%2E215
+values:
+  2021-01-01: 65

policyengine_us/parameters/gov/states/mt/tax/income/exemptions/interest/cap.yaml

@@ -0,0 +1,25 @@
+description: Montana caps the interest income exclusion to this amount, based on filing status.
+metadata:
+  label: Montana senior interest income exclusion cap
+  period: year
+  unit: currency-USD
+  breakdown:
+  - filing_status
+  reference: 
+    - title: 2021 Montana Form 2 | line 3 - Partial Interest Exemption for Taxpayers
+      href: https://mtrevenue.gov/wp-content/uploads/mdocs/form%202%202021%20instructions.pdf#page=24
+    - title: 2022 Montana Form 2 | line 3 - Partial Interest Exemption for Taxpayers
+      href: https://mtrevenue.gov/wp-content/uploads/dlm_uploads/2022/12/Form-2-2022-Instructions.pdf#page=25
+    - title: Administrative Rules of Montana | Income Taxes | § 42.14.215 (2) & (3)
+      href: https://rules.mt.gov/gateway/RuleNo.asp?RN=42%2E15%2E215
+
+SINGLE:
+  2021-01-01: 800
+SEPARATE:
+  2021-01-01: 800
+JOINT:
+  2021-01-01: 1_600
+HEAD_OF_HOUSEHOLD:
+  2021-01-01: 800
+WIDOW:
+  2021-01-01: 800

policyengine_us/parameters/gov/states/mt/tax/income/subtractions/subtractions.yaml

@@ -0,0 +1,14 @@
+description: Montana counts these sources as subtractions.
+values:
+  2021-01-01:
+    - mt_interest_exemption
+metadata:
+  unit: list
+  label: Montana adjusted gross income subtractions
+  reference:
+    - title: 2021 Montana Form 2 | Montana Subtractions Schedule
+      href: https://mtrevenue.gov/wp-content/uploads/mdocs/form%202%202021%20instructions.pdf#page=24
+    - title: 2022 Montana Form 2 | Montana Subtractions Schedule
+      href: https://mtrevenue.gov/wp-content/uploads/dlm_uploads/2022/12/Form-2-2022-Instructions.pdf#page=25
+    - title: Administrative Rules of Montana | Income Taxes | 42.15.2:Montana Additions and Subtractions
+      href: https://rules.mt.gov/gateway/Subchapterhome.asp?scn=42%2E15%2E2

policyengine_us/tests/policy/baseline/gov/states/mt/tax/income/exemptions/mt_interest_exemption.yaml

@@ -0,0 +1,55 @@
+- name: Joint filing, eligible
+  period: 2023
+  input:
+    people:
+      person1:
+        taxable_interest_income: 1_000
+      person2:
+        taxable_interest_income: 900
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+        filing_status: JOINT
+        mt_interest_exemption_eligible: true
+    households:
+      household:
+        state_code: MT
+  output:
+    mt_interest_exemption: 1_600
+
+- name: Joint filing, not eligible
+  period: 2023
+  input:
+    people:
+      person1:
+        taxable_interest_income: 1_000
+      person2:
+        taxable_interest_income: 900
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+        filing_status: JOINT
+        mt_interest_exemption_eligible: false
+    households:
+      household:
+        state_code: MT
+  output:
+    mt_interest_exemption: 0
+
+- name: Single filing, eligible
+  period: 2023
+  input:
+    people:
+      person1:
+        is_tax_unit_head: true
+        taxable_interest_income: 1_000
+    tax_units:
+      tax_unit:
+        members: [person1]
+        filing_status: SINGLE
+        mt_interest_exemption_eligible: true
+    households:
+      household:
+        state_code: MT
+  output:
+    mt_interest_exemption: 800

policyengine_us/tests/policy/baseline/gov/states/mt/tax/income/exemptions/mt_interest_exemption_eligible.yaml

@@ -0,0 +1,44 @@
+- name: both are eligible
+  period: 2023
+  input:
+    people:
+      person1:
+        age: 65
+        is_tax_unit_head_or_spouse: true
+      person2:
+        age: 65
+        is_tax_unit_head_or_spouse: true
+    households:
+      household:
+        state_code: MT
+  output:
+    mt_interest_exemption_eligible: true
+
+- name:  both are eligible, even spouse is under the age
+  period: 2023
+  input:
+    people:
+      person1:
+        age: 62
+        is_tax_unit_head_or_spouse: true
+      person2:
+        age: 65
+        is_tax_unit_head_or_spouse: true
+    households:
+      household:
+        state_code: MT
+  output:
+    mt_interest_exemption_eligible: true
+
+- name: single not eligible
+  period: 2023
+  input:
+    people:
+      person1:
+        age: 62
+        is_tax_unit_head_or_spouse: true
+    households:
+      household:
+        state_code: MT
+  output:
+    mt_interest_exemption_eligible: false

policyengine_us/variables/gov/states/mt/tax/income/exemptions/mt_interest_exemption.py

@@ -0,0 +1,19 @@
+from policyengine_us.model_api import *
+
+
+class mt_interest_exemption(Variable):
+    value_type = float
+    entity = TaxUnit
+    label = "Montana interest exemption"
+    unit = USD
+    definition_period = YEAR
+    reference = "https://mtrevenue.gov/wp-content/uploads/dlm_uploads/2022/12/Form-2-2022-Instructions.pdf#page=25"
+    defined_for = "mt_interest_exemption_eligible"
+
+    def formula(tax_unit, period, parameters):
+        p = parameters(period).gov.states.mt.tax.income.exemptions.interest
+        person = tax_unit.members
+        filing_status = tax_unit("filing_status", period)
+        cap = p.cap[filing_status]
+        interest_income = person("taxable_interest_income", period)
+        return min_(cap, tax_unit.sum(interest_income))

policyengine_us/variables/gov/states/mt/tax/income/exemptions/mt_interest_exemption_eligible.py

@@ -0,0 +1,17 @@
+from policyengine_us.model_api import *
+
+
+class mt_interest_exemption_eligible(Variable):
+    value_type = bool
+    entity = TaxUnit
+    label = "Eligible for the Montana interest exemption"
+    definition_period = YEAR
+    reference = "https://mtrevenue.gov/wp-content/uploads/dlm_uploads/2022/12/Form-2-2022-Instructions.pdf#page=25"
+    defined_for = StateCode.MT
+
+    def formula(tax_unit, period, parameters):
+        person = tax_unit.members
+        p = parameters(period).gov.states.mt.tax.income.exemptions.interest
+        head_or_spouse = person("is_tax_unit_head_or_spouse", period)
+        age = person("age", period)
+        return tax_unit.any(head_or_spouse & (age >= p.age_threshold))

policyengine_us/variables/gov/states/mt/tax/income/subtractions/mt_subtractions.py

@@ -0,0 +1,12 @@
+from policyengine_us.model_api import *
+
+
+class mt_subtractions(Variable):
+    value_type = float
+    entity = TaxUnit
+    label = "Montana subtractions"
+    unit = USD
+    definition_period = YEAR
+    defined_for = StateCode.MT
+
+    adds = "gov.states.mt.tax.income.subtractions.subtractions"