MaxGhenis · Nov 14, 2026 · Nov 12, 2026 · Nov 12, 2026
diff --git a/changelog.d/mt-historical-income-tax-parameters.fixed.md b/changelog.d/mt-historical-income-tax-parameters.fixed.md
@@ -0,0 +1 @@
+Correct Montana's 2017–2020 income tax brackets, exemptions, standard deductions, pension exemption limits, and eligible subtractions.
diff --git a/policyengine_us/parameters/gov/states/mt/tax/income/additions/additions.yaml b/policyengine_us/parameters/gov/states/mt/tax/income/additions/additions.yaml
@@ -1,14 +1,16 @@
 description: Montana counts these sources as additions.
 
 values:
-  2021-01-01:
+  2017-01-01:
     - mt_other_additions
 
 metadata:
   unit: list
   period: year
   label: Montana adjusted gross income additions
   reference:
+    - title: 2017 Montana Form 2 instructions, Schedule I, other additions
+      href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=20
     - title: 2021 Montana Form 2 | Montana Subtractions Schedule
       href: https://revenuefiles.mt.gov/files/Forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2021_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=21
     - title: 2022 Montana Form 2 | Montana Subtractions Schedule

diff --git a/policyengine_us/parameters/gov/states/mt/tax/income/credits/capital_gain/percentage.yaml b/policyengine_us/parameters/gov/states/mt/tax/income/credits/capital_gain/percentage.yaml
@@ -1,10 +1,12 @@
 description: Montana provides a credit for this fraction of the filer's net capital gains.
 values:
-  2021-01-01: 0.02
+  2017-01-01: 0.02
 metadata:
   unit: /1
   label: Montana capital gains credit rate
   reference:
+  - title: 2017 Montana Form 2 instructions, line 47, capital gains tax credit
+    href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=11
   - title: MT Code, Income Tax - Deductions, § 42.4.502 (1)
     href: https://rules.mt.gov/gateway/RuleNo.asp?RN=42%2E4%2E502
   - title: Montana Tax Form 2022 | Nonrefundable Credits Schedule | Line 1

diff --git a/policyengine_us/parameters/gov/states/mt/tax/income/credits/non_refundable.yaml b/policyengine_us/parameters/gov/states/mt/tax/income/credits/non_refundable.yaml
@@ -4,14 +4,16 @@ description: Montana provides the following non-refundable tax credits.
 # so listing the rebate would make it an input to its own cap and create a
 # cycle. The rebate is a refundable payment (mt_refundable_credits).
 values:
-  2021-01-01:
+  2017-01-01:
     - mt_capital_gain_credit
   2024-01-01: []
 metadata:
   unit: list
   period: year
   label: Montana non-refundable tax credits
   reference:
+    - title: 2017 Montana Form 2 instructions, line 47, capital gains tax credit
+      href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=11
     - title: 2023 Montana Form 2 Individual Income Tax Instructions, Net Long-Term Capital Gains Tax Rates
       href: https://revenuefiles.mt.gov/files/Forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2023_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=6
     - title: 2021 Montana Form 2 Individual Income Tax Instructions, Line 19 Nonrefundable Credits

diff --git a/...arameters/gov/states/mt/tax/income/deductions/child_dependent_care_expense/age_limit.yaml b/...arameters/gov/states/mt/tax/income/deductions/child_dependent_care_expense/age_limit.yaml
@@ -1,13 +1,15 @@
 description: Montana limits the child and dependent care expense deduction to expenses for dependents who are incapable of self-care or are below this age.
 
 values:
-  2021-01-01: 15
+  2017-01-01: 15
 
 metadata:
   unit: year
   period: year
   label: Montana Child and Dependent Care Expense deduction age threshold
   reference:
+    - title: 2017 Montana Form 2 instructions, line 19, child and dependent care expenses
+      href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=30
     - title: Mont. Code Ann. § 15-30-2131(1)(c)(i)(A)
       href: https://mca.legmt.gov/bills/2019/mca/title_0150/chapter_0300/part_0210/section_0310/0150-0300-0210-0310.html
     - title: 2022 Montana Form 2 Individual income tax instructions, line 14

diff --git a/...e_us/parameters/gov/states/mt/tax/income/deductions/child_dependent_care_expense/cap.yaml b/...e_us/parameters/gov/states/mt/tax/income/deductions/child_dependent_care_expense/cap.yaml
@@ -7,6 +7,8 @@ metadata:
   unit: currency-USD
   label: Montana Child and Dependent Care Expense Deduction cap
   reference:
+  - title: 2017 Montana Form 2 instructions, line 19, child and dependent care expenses
+    href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=30
   - title: Mont. Code Ann. § 15-30-2131(1)(c)(iv)
     href: https://mca.legmt.gov/bills/2019/mca/title_0150/chapter_0300/part_0210/section_0310/0150-0300-0210-0310.html
   - title: 2021 Montana Form 2441-M, line 2
@@ -16,18 +18,18 @@ metadata:
 
 brackets:
   - threshold:
-      2021-01-01: 0
+      2017-01-01: 0
     amount:
-      2021-01-01: 0
+      2017-01-01: 0
   - threshold:
-      2021-01-01: 1
+      2017-01-01: 1
     amount:
-      2021-01-01: 2_400
+      2017-01-01: 2_400
   - threshold:
-      2021-01-01: 2
+      2017-01-01: 2
     amount:
-      2021-01-01: 3_600
+      2017-01-01: 3_600
   - threshold:
-      2021-01-01: 3
+      2017-01-01: 3
     amount:
-      2021-01-01: 4_800
+      2017-01-01: 4_800
diff --git a/...arameters/gov/states/mt/tax/income/deductions/child_dependent_care_expense/in_effect.yaml b/...arameters/gov/states/mt/tax/income/deductions/child_dependent_care_expense/in_effect.yaml
@@ -1,14 +1,16 @@
 description: Montana uses this indicator to determine whether the child and dependent care expense deduction applies.
 
 values:
-  2021-01-01: true
+  2017-01-01: true
   2024-01-01: false
 
 metadata:
   unit: bool
   period: year
   label: Montana Child and Dependent Care Expense Deduction in effect
   reference:
+    - title: 2017 Montana Form 2 instructions, line 19, child and dependent care expenses
+      href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=30
     - title: SB 399 (2021), Ch. 503, L. 2021, Sec. 65, repealing Mont. Code Ann. § 15-30-2131 effective January 1, 2024
       href: https://web.archive.org/web/20240315074930/https://leg.mt.gov/bills/2021/billpdf/SB0399.pdf#page=96
     - title: Montana 2021 Legislative Review, Table of Code Sections Affected

diff --git a/...arameters/gov/states/mt/tax/income/deductions/child_dependent_care_expense/phase_out.yaml b/...arameters/gov/states/mt/tax/income/deductions/child_dependent_care_expense/phase_out.yaml
@@ -6,6 +6,8 @@ metadata:
   type: marginal_rate
   label: Montana Child and Dependent Care Expense Deduction income limit
   reference:
+    - title: 2017 Montana Form 2 instructions, line 19, child and dependent care expenses
+      href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=30
     # Tax forms only show mathematically derived income limit 
     - title: 2022 Montana Form 2 Individual income tax instruction line 14
       href: https://revenuefiles.mt.gov/files/Forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2022_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=35
@@ -18,10 +20,10 @@ metadata:
 
 brackets:
   - threshold:
-      2021-01-01: 0
+      2017-01-01: 0
     rate:
-      2021-01-01: 0
+      2017-01-01: 0
   - threshold:
-      2021-01-01: 18_000
+      2017-01-01: 18_000
     rate:
-      2021-01-01: 0.5
+      2017-01-01: 0.5
diff --git a/...s/parameters/gov/states/mt/tax/income/deductions/itemized/federal_income_tax/applies.yaml b/...s/parameters/gov/states/mt/tax/income/deductions/itemized/federal_income_tax/applies.yaml
@@ -4,6 +4,8 @@ metadata:
   period: year
   unit: bool
   reference:
+    - title: 2017 Montana Form 2 instructions, lines 7a-7e, federal income tax deduction
+      href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=28
     - title: Montana Tax Reform Update (2024)
       href: https://revenue.mt.gov/montana-tax-simplification-resource-hub
     - title: Montana State Senate Bill 399 (2021)
@@ -12,5 +14,5 @@ metadata:
       href: https://taxsim.nber.org/historical_state_tax_forms/MT/2024/Form_2_2024_Instrux.pdf
 
 values:
-  2021-01-01: true
+  2017-01-01: true
   2024-01-01: false
diff --git a/...ne_us/parameters/gov/states/mt/tax/income/deductions/itemized/federal_income_tax/cap.yaml b/...ne_us/parameters/gov/states/mt/tax/income/deductions/itemized/federal_income_tax/cap.yaml
@@ -1,14 +1,14 @@
 description: Montana caps the federal income tax deduction to this amount, based on filing status.
 JOINT:
-  2021-01-01: 10_000
+  2017-01-01: 10_000
 HEAD_OF_HOUSEHOLD:
-  2021-01-01: 5_000
+  2017-01-01: 5_000
 SURVIVING_SPOUSE:
-  2021-01-01: 5_000
+  2017-01-01: 5_000
 SINGLE:
-  2021-01-01: 5_000
+  2017-01-01: 5_000
 SEPARATE:
-  2021-01-01: 5_000
+  2017-01-01: 5_000
 metadata:
   propagate_metadata_to_children: true
   label: Montana federal income tax deduction cap
@@ -17,6 +17,8 @@ metadata:
   breakdown:
     - filing_status
   reference:
+    - title: 2017 Montana Form 2 instructions, line 7e, federal income tax deduction
+      href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=29
     - title: MT Code § 15-30-2131 (2021) (1)(b)
       href: https://law.justia.com/codes/montana/2021/title-15/chapter-30/part-21/section-15-30-2131/
     - title: 2021 Montana Individual Income Tax Return - Form 2

diff --git a/policyengine_us/parameters/gov/states/mt/tax/income/deductions/itemized/misc_deductions.yaml b/policyengine_us/parameters/gov/states/mt/tax/income/deductions/itemized/misc_deductions.yaml
@@ -4,7 +4,7 @@ description: Montana counts these sources as miscellaneous deductions.
 # separately because its income limit uses the return's own Montana AGI, which
 # differs between a joint return and separate columns (Form 2441-M line 3).
 values:
-  2021-01-01:
+  2017-01-01:
     - casualty_loss_deduction
     # Form 2 itemized deductions line 18 follows federal Schedule A line 16.
     - mt_claim_of_right_deduction
@@ -17,6 +17,10 @@ metadata:
   label: Montana miscellaneous deductions
   period: year
   reference:
+    - title: 2017 Montana Form 2 instructions, Schedule III, line 28
+      href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=31
+    - title: 2017 Montana Form 2 instructions, Schedule III, miscellaneous deductions
+      href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=30
     - title: 2023 Montana Form 2 instructions, itemized deductions line 18
       href: https://revenue.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2023_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=39
     - title: 2024 Montana Form 2 instructions, line 2 and Worksheet A

diff --git a/...ne_us/parameters/gov/states/mt/tax/income/deductions/itemized/spouse_allocation_rate.yaml b/...ne_us/parameters/gov/states/mt/tax/income/deductions/itemized/spouse_allocation_rate.yaml
@@ -16,12 +16,14 @@ values:
   #   convention: each spouse enters one-half of Form 2441-M line 7.
   # The federal rule for separate returns also treats payments from a joint
   # account as paid equally.
-  2021-01-01: 0.5
+  2017-01-01: 0.5
 metadata:
   label: Montana itemized deductions spouse allocation rate
   period: year
   unit: /1
   reference:
+    - title: 2017 Montana Form 2 instructions, line 19, separate-filing care expense allocation
+      href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=30
     - title: Montana Administrative Rule 42.15.524 - Itemized Deductions of Married Taxpayers (archived text, in effect until its repeal effective Jan. 25, 2025)
       href: https://web.archive.org/web/20201030190413/http://www.mtrules.org/gateway/ruleno.asp?RN=42.15.524
     - title: 2022 Montana Form 2 Instructions, Allocation of deductions

diff --git a/...meters/gov/states/mt/tax/income/deductions/itemized/state_specific_deduction_applies.yaml b/...meters/gov/states/mt/tax/income/deductions/itemized/state_specific_deduction_applies.yaml
@@ -4,6 +4,8 @@ metadata:
   period: year
   unit: bool
   reference:
+    - title: 2017 Montana Form 2 instructions, Schedule III, itemized deductions
+      href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=28
     - title: Montana Individual Income Tax Return (Form 2) 2023 | Itemized Deductions Schedule
       href: https://revenuefiles.mt.gov/files/Forms/Montana-Individual-Income-Tax-Return-Form-2/2023_Montana_Individual_Income_Tax_Return_Form_2.pdf#page=7
     - title: 2024 Montana Form 2 Instructions | Discontinued Worksheets and Schedules
@@ -12,5 +14,5 @@ metadata:
       href: https://revenuefiles.mt.gov/files/Forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2024_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=15
 
 values:
-  2021-01-01: true
+  2017-01-01: true
   2024-01-01: false
diff --git a/policyengine_us/parameters/gov/states/mt/tax/income/deductions/standard/cap.yaml b/policyengine_us/parameters/gov/states/mt/tax/income/deductions/standard/cap.yaml
@@ -7,6 +7,14 @@ metadata:
   breakdown:
     - filing_status
   reference:
+    - title: MCA 15-30-2132(1), 2019, standard deduction filing status
+      href: https://mca.legmt.gov/bills/2019/mca/title_0150/chapter_0300/part_0210/section_0320/0150-0300-0210-0320.html
+    - title: 26 USC 2(b)(1), 2017, head-of-household eligibility
+      href: https://www.govinfo.gov/content/pkg/USCODE-2017-title26/html/USCODE-2017-title26-subtitleA-chap1-subchapA-partI-sec2.htm
+    - title: 2021 Montana Form 2 instructions, standard deduction limits for 2017-2020
+      href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2021_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=54
+    - title: 2017 Montana Form 2 instructions, Worksheet V, standard deduction
+      href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=50
     - title: MT Code, Income Tax - Deductions, § 42-15-523 (2)
       href: https://rules.mt.gov/gateway/RuleNo.asp?RN=42%2E15%2E523
     - title: Montana Tax Form 2022 | Standard Deduction | Line 3
@@ -19,22 +27,42 @@ metadata:
       href: https://docs.legmt.gov/download-ticket?ticketId=2f0614a3-8bb9-4b4e-93de-21647c203b7c#page=11
 
 JOINT:
+  2017-01-01: 9_020
+  2018-01-01: 9_160
+  2019-01-01: 9_420
+  2020-01-01: 9_580
   2021-01-01: 9_660
   2022-01-01: 10_180
   2023-01-01: 11_080
 HEAD_OF_HOUSEHOLD:
+  2017-01-01: 9_020
+  2018-01-01: 9_160
+  2019-01-01: 9_420
+  2020-01-01: 9_580
   2021-01-01: 9_660
   2022-01-01: 10_180
   2023-01-01: 11_080
 SURVIVING_SPOUSE:
+  2017-01-01: 4_510
+  2018-01-01: 4_580
+  2019-01-01: 4_710
+  2020-01-01: 4_790
   2021-01-01: 4_830
   2022-01-01: 5_090
   2023-01-01: 5_540
 SINGLE:
+  2017-01-01: 4_510
+  2018-01-01: 4_580
+  2019-01-01: 4_710
+  2020-01-01: 4_790
   2021-01-01: 4_830
   2022-01-01: 5_090
   2023-01-01: 5_540
 SEPARATE:
+  2017-01-01: 4_510
+  2018-01-01: 4_580
+  2019-01-01: 4_710
+  2020-01-01: 4_790
   2021-01-01: 4_830
   2022-01-01: 5_090
   2023-01-01: 5_540
diff --git a/policyengine_us/parameters/gov/states/mt/tax/income/deductions/standard/floor.yaml b/policyengine_us/parameters/gov/states/mt/tax/income/deductions/standard/floor.yaml
@@ -7,6 +7,14 @@ metadata:
   breakdown:
     - filing_status
   reference:
+    - title: MCA 15-30-2132(1), 2019, standard deduction filing status
+      href: https://mca.legmt.gov/bills/2019/mca/title_0150/chapter_0300/part_0210/section_0320/0150-0300-0210-0320.html
+    - title: 26 USC 2(b)(1), 2017, head-of-household eligibility
+      href: https://www.govinfo.gov/content/pkg/USCODE-2017-title26/html/USCODE-2017-title26-subtitleA-chap1-subchapA-partI-sec2.htm
+    - title: 2021 Montana Form 2 instructions, standard deduction limits for 2017-2020
+      href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2021_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=54
+    - title: 2017 Montana Form 2 instructions, Worksheet V, standard deduction
+      href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=50
     - title: MT Code, Income Tax - Deductions, § 42-15-523 (2)
       href: https://rules.mt.gov/gateway/RuleNo.asp?RN=42%2E15%2E523
     - title: Montana Tax Form 2022 | Standard Deduction | Line 5
@@ -19,22 +27,42 @@ metadata:
       href: https://docs.legmt.gov/download-ticket?ticketId=2f0614a3-8bb9-4b4e-93de-21647c203b7c
 
 JOINT:
+  2017-01-01: 4_000
+  2018-01-01: 4_060
+  2019-01-01: 4_180
+  2020-01-01: 4_260
   2021-01-01: 4_280
   2022-01-01: 4_520
   2023-01-01: 4_920
 HEAD_OF_HOUSEHOLD:
+  2017-01-01: 4_000
+  2018-01-01: 4_060
+  2019-01-01: 4_180
+  2020-01-01: 4_260
   2021-01-01: 4_280
   2022-01-01: 4_520
   2023-01-01: 4_920
 SURVIVING_SPOUSE:
+  2017-01-01: 2_000
+  2018-01-01: 2_030
+  2019-01-01: 2_090
+  2020-01-01: 2_130
   2021-01-01: 2_140
   2022-01-01: 2_260
   2023-01-01: 2_460
 SINGLE:
+  2017-01-01: 2_000
+  2018-01-01: 2_030
+  2019-01-01: 2_090
+  2020-01-01: 2_130
   2021-01-01: 2_140
   2022-01-01: 2_260
   2023-01-01: 2_460
 SEPARATE:
+  2017-01-01: 2_000
+  2018-01-01: 2_030
+  2019-01-01: 2_090
+  2020-01-01: 2_130
   2021-01-01: 2_140
   2022-01-01: 2_260
   2023-01-01: 2_460
diff --git a/policyengine_us/parameters/gov/states/mt/tax/income/deductions/standard/rate.yaml b/policyengine_us/parameters/gov/states/mt/tax/income/deductions/standard/rate.yaml
@@ -1,11 +1,13 @@
 description: Montana provides a standard deduction equal to this percentage of Montana adjusted gross income, subject to minimum and maximum values.
 values:
-  2021-01-01: 0.2
+  2017-01-01: 0.2
 metadata:
   period: year
   unit: /1
   label: Montana standard deduction rate
   reference:
+  - title: 2017 Montana Form 2 instructions, Worksheet V, standard deduction
+    href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=50
   - title: MT Code, Income Tax - Deductions, § 42-15-512 (2)
     href: https://rules.mt.gov/gateway/RuleNo.asp?RN=42%2E15%2E523
   - title: Montana Tax Form 2022 | Standard Deduction | Line 2

diff --git a/...meters/gov/states/mt/tax/income/deductions/standard/state_specific_deduction_applies.yaml b/...meters/gov/states/mt/tax/income/deductions/standard/state_specific_deduction_applies.yaml
@@ -4,6 +4,8 @@ metadata:
   period: year
   unit: bool
   reference:
+    - title: 2017 Montana Form 2 instructions, Worksheet V, standard deduction
+      href: https://revenuefiles.mt.gov/files/forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2017_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=50
     - title: MT Code, Income Tax - Deductions, § 42-15-523 (2)
       href: https://rules.mt.gov/gateway/RuleNo.asp?RN=42%2E15%2E523
     - title: Montana Tax Form 2023 | Exemptions | Standard Deduction Worksheet
@@ -14,5 +16,5 @@ metadata:
       href: https://revenuefiles.mt.gov/files/Forms/Montana-Individual-Income-Tax-Return-Form-2-Instructions/2024_Montana_Individual_Income_Tax_Return_Form_2_Instructions.pdf#page=8
 
 values:
-  2021-01-01: true
+  2017-01-01: true
   2024-01-01: false
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Correct Montana's 2017–2020 income tax brackets, exemptions, standard deductions, pension exemption limits, and eligible subtractions.