PolicyEngine · MaxGhenis · Jan 3, 2026
diff --git a/changelog_entry.yaml b/changelog_entry.yaml
@@ -0,0 +1,8 @@
+- bump: minor
+  changes:
+    changed:
+      - Consolidated itemized deduction limitation parameters from `reduction/` to `limitation/` folder for cleaner organization.
+      - Renamed OBBB (One Big Beautiful Bill Act) itemized deduction parameters from `amended_structure/` to `obbb/` for clarity.
+      - Updated federal and Hawaii itemized deduction variables to use the consolidated parameter path.
+    fixed:
+      - Fixed YAML syntax errors in several parameter files (tabs replaced with spaces, URLs properly quoted).
diff --git a/policyengine_us/parameters/gov/irs/deductions/itemized/limitation/applicable_amount.yaml b/policyengine_us/parameters/gov/irs/deductions/itemized/limitation/applicable_amount.yaml
@@ -1,6 +1,8 @@
 description: The US limits the itemized deductions to filers with adjusted gross income over this amount, based on filing status.
 JOINT:
-  values: 
+  values:
+    2009-01-01: 250_200
+    2010-01-01: .inf
     2013-01-01: 300_000
     2014-01-01: 305_050
     2015-01-01: 309_900
@@ -26,6 +28,8 @@ JOINT:
         interval: 50
 SINGLE:
   values:
+    2009-01-01: 166_800
+    2010-01-01: .inf
     2013-01-01: 250_000
     2014-01-01: 254_200
     2015-01-01: 258_250
@@ -51,6 +55,8 @@ SINGLE:
         interval: 50
 SEPARATE:
   values:
+    2009-01-01: 125_100
+    2010-01-01: .inf
     2013-01-01: 150_000
     2014-01-01: 152_525
     2015-01-01: 154_950
@@ -76,6 +82,8 @@ SEPARATE:
         interval: 50
 HEAD_OF_HOUSEHOLD:
   values:
+    2009-01-01: 208_500
+    2010-01-01: .inf
     2013-01-01: 275_000
     2014-01-01: 279_650
     2015-01-01: 284_050
@@ -99,8 +107,10 @@ HEAD_OF_HOUSEHOLD:
       rounding:
         type: downwards
         interval: 50
-SURVIVING_SPOUSE: # Same as joint  
+SURVIVING_SPOUSE: # Same as joint
   values:
+    2009-01-01: 250_200
+    2010-01-01: .inf
     2013-01-01: 300_000
     2014-01-01: 305_050
     2015-01-01: 309_900
@@ -131,9 +141,11 @@ metadata:
   breakdown:
   - filing_status
   reference:
-    # This section of the legal code was repealed between 2018 and 2026.
+    # This section of the legal code was repealed between 2010-2012 and 2018-2025.
     - title: 26 U.S. Code § 68 - Overall limitation on itemized deductions (b)(1)
       href: https://www.law.cornell.edu/uscode/text/26/68#b_1
+    - title: 2009 Form 1040 - Limit on Itemized Deductions
+      href: https://www.irs.gov/pub/irs-prior/i1040gi--2009.pdf#page=6
     - title: 2013 Instruction 1040 Schedule A
       href: https://www.irs.gov/pub/irs-prior/i1040sca--2013.pdf#page=13
     - title: 2014 Instruction 1040 Schedule A

diff --git a/...eductions/itemized/reduction/applies.yaml → ...ductions/itemized/limitation/applies.yaml b/...eductions/itemized/reduction/applies.yaml → ...ductions/itemized/limitation/applies.yaml
@@ -1,4 +1,4 @@
-description: The itemized deductions reduction applies if this is true.
+description: The itemized deductions limitation applies if this is true.
 
 values:
   2009-01-01: true
@@ -10,7 +10,7 @@ values:
 metadata:
   unit: bool
   period: year
-  label: Itemized deductions reduction applies
+  label: Itemized deductions limitation applies
   reference:
-    - title: 26 U.S. Code § 68 - Overall limitation on itemized deductions, (a)(2) 
+    - title: 26 U.S. Code § 68 - Overall limitation on itemized deductions, (a)(2)
       href: https://www.law.cornell.edu/uscode/text/26/68
diff --git a/.../reduction/amended_structure/applies.yaml → ...ons/itemized/limitation/obbb/applies.yaml b/.../reduction/amended_structure/applies.yaml → ...ons/itemized/limitation/obbb/applies.yaml
@@ -1,4 +1,4 @@
-description: The IRS reduces the itemized deductions at an amended structure, if this is true.
+description: The One Big Beautiful Bill Act itemized deductions limitation structure applies, if this is true.
 
 values:
   2009-01-01: false
@@ -7,7 +7,7 @@ values:
 metadata:
   unit: bool
   period: year
-  label: Itemized deductions amended reduction structure applies
+  label: OBBB itemized deductions limitation applies
   reference:
     - title: H.R.1 - One Big Beautiful Bill Act
       href: https://www.congress.gov/bill/119th-congress/house-bill/1/text
diff --git a/policyengine_us/parameters/gov/irs/deductions/itemized/limitation/obbb/rate.yaml b/policyengine_us/parameters/gov/irs/deductions/itemized/limitation/obbb/rate.yaml
@@ -0,0 +1,12 @@
+description: The One Big Beautiful Bill Act phases out itemized deductions at this rate of the lesser of the itemized deductions or taxable income above the highest income tax rate threshold.
+
+values:
+  0000-01-01: 0.05405405 # 2/37
+
+metadata:
+  unit: /1
+  period: year
+  label: OBBB itemized deductions limitation rate
+  reference:
+    - title: H.R.1 - One Big Beautiful Bill Act
+      href: https://www.congress.gov/bill/119th-congress/house-bill/1/text
diff --git a/policyengine_us/parameters/gov/irs/deductions/itemized/reduction/agi_threshold.yaml b/policyengine_us/parameters/gov/irs/deductions/itemized/reduction/agi_threshold.yaml
diff --git a/policyengine_us/parameters/gov/irs/deductions/itemized/reduction/amended_structure/rate.yaml b/policyengine_us/parameters/gov/irs/deductions/itemized/reduction/amended_structure/rate.yaml
diff --git a/policyengine_us/parameters/gov/irs/deductions/itemized/reduction/rate/base.yaml b/policyengine_us/parameters/gov/irs/deductions/itemized/reduction/rate/base.yaml
diff --git a/policyengine_us/parameters/gov/irs/deductions/itemized/reduction/rate/excess_agi.yaml b/policyengine_us/parameters/gov/irs/deductions/itemized/reduction/rate/excess_agi.yaml
diff --git a/policyengine_us/parameters/gov/states/ca/cdss/tanf/cash/monthly_payment/max_au_size.yaml b/policyengine_us/parameters/gov/states/ca/cdss/tanf/cash/monthly_payment/max_au_size.yaml
@@ -6,8 +6,9 @@ metadata:
   label: California CalWORKs maximum assistance unit size for payment standards
   reference:
     - title: County of San Diego CalWORKS Program Guide | CalWORKs Payment Standards Chart
-      href: [https://hhsaprogramguides.sandiegocounty.gov/CalWORKS/44-300/CalWORKs_Payment_Standards/G_CalWORKs_Payment_Standards.pdf,
-      https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=WIC&sectionNum=11450.]
+      href: "https://hhsaprogramguides.sandiegocounty.gov/CalWORKS/44-300/CalWORKs_Payment_Standards/G_CalWORKs_Payment_Standards.pdf"
+    - title: California Welfare and Institutions Code Section 11450
+      href: "https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=WIC&sectionNum=11450."
 
 values:
   2023-01-01: 10 # Actual date: 2023-10-01
diff --git a/policyengine_us/parameters/gov/states/ca/cdss/tanf/cash/region1_counties.yaml b/policyengine_us/parameters/gov/states/ca/cdss/tanf/cash/region1_counties.yaml
@@ -6,8 +6,9 @@ metadata:
   label: California CalWORKs region 1 counties
   reference:
     - title: Los Angeles Department of Public Social Services E-Policy | CalWORKs Region Definiton
-      href: [http://epolicy.dpss.lacounty.gov/epolicy/epolicy/server/general/projects_responsive/ePolicyMaster/index.htm?&area=general&type=responsivehelp&ctxid=&project=ePolicyMaster#t=mergedProjects%2FCalWORKs%2FCalWORKs%2F44-212_Minimum_Basic_Standard_of_Adequate_Care%2F44-212_Minimum_Basic_Standard_of_Adequate_Care.htm%23Definitionsbc-4&rhtocid=_3_1_7_20_3,
-            https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=WIC&sectionNum=11452.018.]
+      href: "http://epolicy.dpss.lacounty.gov/epolicy/epolicy/server/general/projects_responsive/ePolicyMaster/index.htm?&area=general&type=responsivehelp&ctxid=&project=ePolicyMaster#t=mergedProjects%2FCalWORKs%2FCalWORKs%2F44-212_Minimum_Basic_Standard_of_Adequate_Care%2F44-212_Minimum_Basic_Standard_of_Adequate_Care.htm%23Definitionsbc-4&rhtocid=_3_1_7_20_3"
+    - title: California Welfare and Institutions Code Section 11452.018
+      href: "https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=WIC&sectionNum=11452.018."
 values:
   2023-01-01: # Actual date: 2023-07-01
     - ALAMEDA_COUNTY_CA

diff --git a/...engine_us/parameters/gov/states/ma/tax/income/credits/child_and_family/dependent_cap.yaml b/...engine_us/parameters/gov/states/ma/tax/income/credits/child_and_family/dependent_cap.yaml
@@ -8,7 +8,7 @@ metadata:
       href: https://www.mass.gov/doc/2021-form-1-instructions/download#page=17
     - title: Form 1 2022 Massachusetts Resident Income Tax (line 46)
       href: https://www.mass.gov/doc/2022-form-1-instructions/download#page=17
-    - title: Law	Result Summary Part I Title IX Chapter 62 Section 6 (y) (ii) (B)
+    - title: Law Result Summary Part I Title IX Chapter 62 Section 6 (y) (ii) (B)
       href: https://malegislature.gov/Laws/GeneralLaws/PartI/TitleIX/Chapter62/Section6 
     - title: Form 1 2023 Massachusetts Resident Income Tax (line 46)
       href: https://www.mass.gov/doc/2023-form-1-instructions/download#page=17

diff --git a/policyengine_us/parameters/gov/states/me/tax/income/main/head_of_household.yaml b/policyengine_us/parameters/gov/states/me/tax/income/main/head_of_household.yaml
@@ -16,9 +16,9 @@ metadata:
       href: https://www.maine.gov/revenue/sites/maine.gov.revenue/files/inline-files/22_1040me_dwnld_ff.pdf#page=2
     - title: Maine 2022 Individual Income Tax Rate Schedules
       href: https://www.maine.gov/revenue/sites/maine.gov.revenue/files/inline-files/22_1040me_tax_tables.pdf#page=5
-    - title: Maine 2023	Individual Income Tax Rate Schedules
+    - title: Maine 2023 Individual Income Tax Rate Schedules
       href: https://www.maine.gov/revenue/sites/maine.gov.revenue/files/inline-files/23_1040me_tax_tables.pdf#page=5
-    - title: Maine 2024	Individual Income Tax Rate Schedules
+    - title: Maine 2024 Individual Income Tax Rate Schedules
       href: https://www.maine.gov/revenue/sites/maine.gov.revenue/files/inline-files/ind_tax_rate_sched_2024.pdf
 
 brackets:

diff --git a/policyengine_us/parameters/gov/states/me/tax/income/main/joint.yaml b/policyengine_us/parameters/gov/states/me/tax/income/main/joint.yaml
@@ -16,9 +16,9 @@ metadata:
       href: https://www.maine.gov/revenue/sites/maine.gov.revenue/files/inline-files/22_1040me_dwnld_ff.pdf#page=2
     - title: Maine 2022 Individual Income Tax Rate Schedules
       href: https://www.maine.gov/revenue/sites/maine.gov.revenue/files/inline-files/22_1040me_tax_tables.pdf#page=5
-    - title: Maine 2023	Individual Income Tax Rate Schedules
+    - title: Maine 2023 Individual Income Tax Rate Schedules
       href: https://www.maine.gov/revenue/sites/maine.gov.revenue/files/inline-files/23_1040me_tax_tables.pdf#page=5
-    - title: Maine 2024	Individual Income Tax Rate Schedules
+    - title: Maine 2024 Individual Income Tax Rate Schedules
       href: https://www.maine.gov/revenue/sites/maine.gov.revenue/files/inline-files/ind_tax_rate_sched_2024.pdf
 brackets:
   - threshold:

diff --git a/policyengine_us/parameters/gov/states/me/tax/income/main/separate.yaml b/policyengine_us/parameters/gov/states/me/tax/income/main/separate.yaml
@@ -16,9 +16,9 @@ metadata:
       href: https://www.maine.gov/revenue/sites/maine.gov.revenue/files/inline-files/22_1040me_dwnld_ff.pdf#page=2
     - title: Maine 2022 Individual Income Tax Rate Schedules
       href: https://www.maine.gov/revenue/sites/maine.gov.revenue/files/inline-files/22_1040me_tax_tables.pdf#page=5
-    - title: Maine 2023	Individual Income Tax Rate Schedules
+    - title: Maine 2023 Individual Income Tax Rate Schedules
       href: https://www.maine.gov/revenue/sites/maine.gov.revenue/files/inline-files/23_1040me_tax_tables.pdf#page=5
-    - title: Maine 2024	Individual Income Tax Rate Schedules
+    - title: Maine 2024 Individual Income Tax Rate Schedules
       href: https://www.maine.gov/revenue/sites/maine.gov.revenue/files/inline-files/ind_tax_rate_sched_2024.pdf
 brackets:
   - threshold:

diff --git a/policyengine_us/parameters/gov/states/me/tax/income/main/single.yaml b/policyengine_us/parameters/gov/states/me/tax/income/main/single.yaml
@@ -16,9 +16,9 @@ metadata:
       href: https://www.maine.gov/revenue/sites/maine.gov.revenue/files/inline-files/22_1040me_dwnld_ff.pdf#page=2
     - title: Maine 2022 Individual Income Tax Rate Schedules
       href: https://www.maine.gov/revenue/sites/maine.gov.revenue/files/inline-files/22_1040me_tax_tables.pdf#page=5
-    - title: Maine 2023	Individual Income Tax Rate Schedules
+    - title: Maine 2023 Individual Income Tax Rate Schedules
       href: https://www.maine.gov/revenue/sites/maine.gov.revenue/files/inline-files/23_1040me_tax_tables.pdf#page=5
-    - title: Maine 2024	Individual Income Tax Rate Schedules
+    - title: Maine 2024 Individual Income Tax Rate Schedules
       href: https://www.maine.gov/revenue/sites/maine.gov.revenue/files/inline-files/ind_tax_rate_sched_2024.pdf
 brackets:
   - threshold: