PolicyEngine · hua7450 · Jan 19, 2026 · Jan 19, 2026 · Jan 19, 2026 · Jan 22, 2026
diff --git a/changelog_entry.yaml b/changelog_entry.yaml
@@ -0,0 +1,4 @@
+- bump: patch
+  changes:
+    changed:
+      - Add historical values to Washington TANF parameters.
diff --git a/.../parameters/gov/states/wa/dshs/tanf/income/deductions/earned_income_disregard/amount.yaml b/.../parameters/gov/states/wa/dshs/tanf/income/deductions/earned_income_disregard/amount.yaml
@@ -1,7 +1,7 @@
 description: Washington deducts this amount from the household's total gross earned income under the Temporary Assistance for Needy Families program.
 
 values:
-  2024-01-01: 500
+  2024-08-01: 500
 
 metadata:
   unit: currency-USD
@@ -10,5 +10,5 @@ metadata:
   reference:
     - title: WAC 388-450-0170(2) - Deducting the first $500 of earned income
       href: https://app.leg.wa.gov/wac/default.aspx?cite=388-450-0170
-    - title: DSHS Eligibility A-Z Manual, Income - Earned Income Deductions
-      href: https://www.dshs.wa.gov/esa/income-table-contents/budgeting
+    - title: HB 1447 (2023 c 418) Sec 5
+      href: https://lawfilesext.leg.wa.gov/biennium/2023-24/Pdf/Bills/Session%20Laws/House/1447-S2.SL.pdf#page=10
diff --git a/...rameters/gov/states/wa/dshs/tanf/income/deductions/earned_income_disregard/in_effect.yaml b/...rameters/gov/states/wa/dshs/tanf/income/deductions/earned_income_disregard/in_effect.yaml
@@ -0,0 +1,15 @@
+description: Washington applies a flat earnings disregard to earned income under the Temporary Assistance for Needy Families program if this is true.
+
+values:
+  1998-09-01: false
+  2024-08-01: true
+
+metadata:
+  unit: bool
+  period: month
+  label: Washington TANF flat earnings disregard in effect
+  reference:
+    - title: WAC 388-450-0170 - Earned income deductions
+      href: https://app.leg.wa.gov/wac/default.aspx?cite=388-450-0170
+    - title: HB 1447 (2023 c 418) Sec 5
+      href: https://lawfilesext.leg.wa.gov/biennium/2023-24/Pdf/Bills/Session%20Laws/House/1447-S2.SL.pdf#page=10
diff --git a/...ome_disregard/percentage_disregarded.yaml → ...uctions/earned_income_disregard/rate.yaml b/...ome_disregard/percentage_disregarded.yaml → ...uctions/earned_income_disregard/rate.yaml
@@ -1,7 +1,7 @@
 description: Washington disregards this share of remaining earned income under the Temporary Assistance for Needy Families program.
 
 values:
-  2024-01-01: 0.5
+  1998-09-01: 0.5
 
 metadata:
   unit: /1
@@ -10,5 +10,3 @@ metadata:
   reference:
     - title: WAC 388-450-0170(3) - Subtract 50% of remaining earned income
       href: https://app.leg.wa.gov/wac/default.aspx?cite=388-450-0170
-    - title: DSHS Eligibility A-Z Manual, Income - Earned Income Deductions
-      href: https://www.dshs.wa.gov/esa/income-table-contents/budgeting
diff --git a/policyengine_us/parameters/gov/states/wa/dshs/tanf/income/limit.yaml b/policyengine_us/parameters/gov/states/wa/dshs/tanf/income/limit.yaml
@@ -1,38 +1,86 @@
 description: Washington sets these gross earned income limits for the Temporary Assistance for Needy Families program.
-# Note: These values follow the formula: Income Limit = (Payment Standard × 2) + $500
-# This represents the break-even point where countable income equals the payment standard,
-# resulting in $0 benefit. While mathematically derived, WAC 388-478-0035 publishes these
-# as a table rather than a formula, so we preserve the table structure here.
+# Note: These values appear to follow a mathematical relationship with payment standards
+# (Income Limit ≈ Payment Standard × 2, plus $500 after Aug 1, 2024), but no legal code
+# explicitly states this formula. WAC 388-478-0035 publishes these as a table.
+# Values here are taken directly from the published WSR tables.
 
 metadata:
   unit: currency-USD
   period: month
   label: Washington TANF maximum gross earned income limit
   breakdown:
     - range(1, 11)
-  breakdown_labels:
+  breakdown_label:
     - Assistance unit size
   reference:
     - title: WAC 388-478-0035 - Maximum earned income limits for TANF, SFA, PWA, and RCA
       href: https://app.leg.wa.gov/wac/default.aspx?cite=388-478-0035
+    - title: WAC 388-478-0035 Maximum earned income limits for TANF, SFA, PWA, and RCA. 2016
+      href: https://lawfilesext.leg.wa.gov/law/wsr/2016/01/16-01-093.htm
+    - title: WAC 388-478-0035 Maximum earned income limits for TANF, SFA, PWA, and RCA. 2018
+      href: https://lawfilesext.leg.wa.gov/law/wsr/2018/09/18-09-088.htm
+    - title: WAC 388-478-0035 Maximum earned income limits for TANF, SFA, PWA, and RCA. 2021
+      href: https://lawfilesext.leg.wa.gov/law/wsr/2021/21/21-21-054.htm
+    - title: WAC 388-478-0035 Maximum earned income limits for TANF, SFA, PWA, and RCA. 2024
+      href: https://lawfilesext.leg.wa.gov/law/wsr/2023/23/23-23-054.htm
 
 1:
-  2024-01-01: 1_400
+  2016-02-01: 665
+  2018-07-01: 726
+  2021-07-01: 834
+  2024-01-01: 900
+  2024-08-01: 1_400
 2:
-  2024-01-01: 1_640
+  2016-02-01: 839
+  2018-07-01: 918
+  2021-07-01: 1_056
+  2024-01-01: 1_140
+  2024-08-01: 1_640
 3:
-  2024-01-01: 1_912
+  2016-02-01: 1_042
+  2018-07-01: 1_138
+  2021-07-01: 1_308
+  2024-01-01: 1_412
+  2024-08-01: 1_912
 4:
-  2024-01-01: 2_166
+  2016-02-01: 1_225
+  2018-07-01: 1_340
+  2021-07-01: 1_542
+  2024-01-01: 1_666
+  2024-08-01: 2_166
 5:
-  2024-01-01: 2_418
+  2016-02-01: 1_413
+  2018-07-01: 1_544
+  2021-07-01: 1_776
+  2024-01-01: 1_918
+  2024-08-01: 2_418
 6:
-  2024-01-01: 2_680
+  2016-02-01: 1_604
+  2018-07-01: 1_754
+  2021-07-01: 2_018
+  2024-01-01: 2_180
+  2024-08-01: 2_680
 7:
-  2024-01-01: 3_016
+  2016-02-01: 1_853
+  2018-07-01: 2_026
+  2021-07-01: 2_330
+  2024-01-01: 2_516
+  2024-08-01: 3_016
 8:
-  2024-01-01: 3_284
+  2016-02-01: 2_051
+  2018-07-01: 2_242
+  2021-07-01: 2_578
+  2024-01-01: 2_784
+  2024-08-01: 3_284
 9:
-  2024-01-01: 3_558
+  2016-02-01: 2_252
+  2018-07-01: 2_462
+  2021-07-01: 2_832
+  2024-01-01: 3_058
+  2024-08-01: 3_558
 10:
-  2024-01-01: 3_824
+  2016-02-01: 2_448
+  2018-07-01: 2_676
+  2021-07-01: 3_078
+  2024-01-01: 3_324
+  2024-08-01: 3_824
diff --git a/policyengine_us/parameters/gov/states/wa/dshs/tanf/maximum_family_size.yaml b/policyengine_us/parameters/gov/states/wa/dshs/tanf/maximum_family_size.yaml
@@ -1,7 +1,7 @@
 description: Washington defines payment standards and income limits for family sizes up to this maximum under the Temporary Assistance for Needy Families program.
 
 values:
-  2024-01-01: 10
+  2016-01-01: 10
 
 metadata:
   unit: person

diff --git a/policyengine_us/parameters/gov/states/wa/dshs/tanf/payment_standard/amount.yaml b/policyengine_us/parameters/gov/states/wa/dshs/tanf/payment_standard/amount.yaml
@@ -6,29 +6,68 @@ metadata:
   label: Washington TANF payment standard
   breakdown:
     - range(1, 11)
-  breakdown_labels:
+  breakdown_label:
     - Assistance unit size
   reference:
     - title: WAC 388-478-0020 - Payment standards for TANF, SFA, and RCA
       href: https://app.leg.wa.gov/wac/default.aspx?cite=388-478-0020
+    - title: WAC 388-478-0020 Payment standards for TANF, SFA, and RCA. 2016
+      href: https://lawfilesext.leg.wa.gov/law/wsr/2016/01/16-01-093.htm
+    - title: WAC 388-478-0020 Payment standards for TANF, SFA, and RCA. 2018
+      href: https://lawfilesext.leg.wa.gov/law/wsr/2018/09/18-09-088.htm
+    - title: WAC 388-478-0020 Payment standards for TANF, SFA, and RCA. 2021
+      href: https://lawfilesext.leg.wa.gov/law/wsr/2021/21/21-21-054.htm
+
+# Note: Values before Oct 25, 2020 are for households "with shelter costs".
+# WSR 20-20-007 eliminated the shelter cost distinction; all households now use these amounts.
 
 1:
+  2016-02-01: 332
+  2018-07-01: 363
+  2021-07-01: 417
   2024-01-01: 450
 2:
+  2016-02-01: 420
+  2018-07-01: 459
+  2021-07-01: 528
   2024-01-01: 570
 3:
+  2016-02-01: 521
+  2018-07-01: 569
+  2021-07-01: 654
   2024-01-01: 706
 4:
+  2016-02-01: 613
+  2018-07-01: 670
+  2021-07-01: 771
   2024-01-01: 833
 5:
+  2016-02-01: 706
+  2018-07-01: 772
+  2021-07-01: 888
   2024-01-01: 959
 6:
+  2016-02-01: 802
+  2018-07-01: 877
+  2021-07-01: 1_009
   2024-01-01: 1_090
 7:
+  2016-02-01: 927
+  2018-07-01: 1_013
+  2021-07-01: 1_165
   2024-01-01: 1_258
 8:
+  2016-02-01: 1_026
+  2018-07-01: 1_121
+  2021-07-01: 1_289
   2024-01-01: 1_392
 9:
+  2016-02-01: 1_126
+  2018-07-01: 1_231
+  2021-07-01: 1_416
   2024-01-01: 1_529
 10:
+  2016-02-01: 1_224
+  2018-07-01: 1_338
+  2021-07-01: 1_539
   2024-01-01: 1_662
diff --git a/policyengine_us/parameters/gov/states/wa/dshs/tanf/payment_standard/maximum_amount.yaml b/policyengine_us/parameters/gov/states/wa/dshs/tanf/payment_standard/maximum_amount.yaml
diff --git a/policyengine_us/parameters/gov/states/wa/dshs/tanf/resource_limit.yaml b/policyengine_us/parameters/gov/states/wa/dshs/tanf/resource_limit.yaml
@@ -1,15 +1,24 @@
 description: Washington limits the Temporary Assistance for Needy Families program to households with countable resources up to this amount.
 
 values:
-  2022-01-01: 6_000
-  2024-01-01: 12_000
+  1998-09-01: 1_000
+  2019-02-01: 6_000
+  2024-02-01: 12_000
+
+# Note: Before Feb 1, 2019, Washington had a two-tier resource limit structure:                                                                                                 
+  # - Applicants: up to $1,000                                                                                                                                                    
+  # - Recipients: up to $1,000 plus an additional $3,000 in savings accounts                                                                                                      
+  # This file uses the applicant limit ($1,000) for the pre-2019 period.                                                                                                          
+  # E2SHB 1831 (2018) simplified this to a single $6,000 limit for all.
 
 metadata:
   unit: currency-USD
   period: year
   label: Washington TANF resource limit
   reference:
-    - title: Washington TANF State Plan 2022, page 13 - $6,000 cash resource limit
-      href: https://workfirst.wa.gov/sites/default/files/public/TANF_stateplan_2022_final.pdf#page=13
+    - title: WAC 388-470-0005 - Resource limits for cash assistance
+      href: https://app.leg.wa.gov/wac/default.aspx?cite=388-470-0005
+    - title: E2SHB 1831 (2018) - Resource limit increased to $6,000 effective Feb 1, 2019
+      href: https://app.leg.wa.gov/billsummary?BillNumber=1831&Year=2017
     - title: HB 1447 (2023 c 418) - Increased asset limit to $12,000 effective Feb 1, 2024
       href: https://app.leg.wa.gov/billsummary?BillNumber=1447&Year=2023
diff --git a/...ne_us/tests/policy/baseline/gov/states/wa/dshs/tanf/benefit/wa_tanf_payment_standard.yaml b/...ne_us/tests/policy/baseline/gov/states/wa/dshs/tanf/benefit/wa_tanf_payment_standard.yaml
@@ -46,3 +46,59 @@
     spm_unit_size: 3
   output:
     wa_tanf_payment_standard: 0
+
+# Historical tests - verify 2016 values apply in early 2018
+- name: Case 7, family size 1 in 2018-01.
+  period: 2018-01
+  input:
+    state_code: WA
+    spm_unit_size: 1
+  output:
+    # Uses 2016-02-01 value (before 2018-07-01 update)
+    wa_tanf_payment_standard: 332
+
+- name: Case 8, family size 3 in 2018-01.
+  period: 2018-01
+  input:
+    state_code: WA
+    spm_unit_size: 3
+  output:
+    # Uses 2016-02-01 value (before 2018-07-01 update)
+    wa_tanf_payment_standard: 521
+
+- name: Case 9, family size 10 in 2018-01.
+  period: 2018-01
+  input:
+    state_code: WA
+    spm_unit_size: 10
+  output:
+    # Uses 2016-02-01 value (before 2018-07-01 update)
+    wa_tanf_payment_standard: 1_224
+
+# Historical tests - verify 2021 values apply in 2022
+- name: Case 10, family size 1 in 2022-01.
+  period: 2022-01
+  input:
+    state_code: WA
+    spm_unit_size: 1
+  output:
+    # Uses 2021-07-01 value (15% increase)
+    wa_tanf_payment_standard: 417
+
+- name: Case 11, family size 3 in 2022-01.
+  period: 2022-01
+  input:
+    state_code: WA
+    spm_unit_size: 3
+  output:
+    # Uses 2021-07-01 value (15% increase)
+    wa_tanf_payment_standard: 654
+
+- name: Case 12, family size 10 in 2022-01.
+  period: 2022-01
+  input:
+    state_code: WA
+    spm_unit_size: 10
+  output:
+    # Uses 2021-07-01 value (15% increase)
+    wa_tanf_payment_standard: 1_539