diff --git a/changelog_entry.yaml b/changelog_entry.yaml
index e69de29bb2d..bf79e9338c6 100644
--- a/changelog_entry.yaml
+++ b/changelog_entry.yaml
@@ -0,0 +1,6 @@
+- bump: patch
+  changes:
+    added:
+      - Add historical TANF parameter data for DE, MO, RI, SD (pre-2018 values).
+      - Add PA TANF Work Expense Reimbursement (WER) for 2009-2020 era.
+      - Add PA TANF work expense mechanism toggle (uses_deduction parameter).
diff --git a/policyengine_us/parameters/gov/states/de/dhss/tanf/benefit/deficit_rate.yaml b/policyengine_us/parameters/gov/states/de/dhss/tanf/benefit/deficit_rate.yaml
index 955f70aa6c1..c0262a642a6 100644
--- a/policyengine_us/parameters/gov/states/de/dhss/tanf/benefit/deficit_rate.yaml
+++ b/policyengine_us/parameters/gov/states/de/dhss/tanf/benefit/deficit_rate.yaml
@@ -1,7 +1,7 @@
 description: Delaware uses this share of the deficit to calculate the grant remainder under the Temporary Assistance for Needy Families program.
 
 values:
-  2024-10-01: 0.5
+  2011-10-01: 0.5
 
 metadata:
   unit: /1
@@ -10,5 +10,7 @@ metadata:
   reference:
     - title: 16 Del. Admin. Code SS 4000-4008.1.1 Step 3 TANF GRANT COMPUTATION
       href: https://www.law.cornell.edu/regulations/delaware/16-Del-Admin-Code-SS-4000-4008
+    - title: Delaware TANF State Plan 2011 - Exhibit 1 and Exhibit 2
+      href: https://dhss.delaware.gov/wp-content/uploads/sites/11/dss/pdf/tanf_ffy2012_stateplan.pdf#page=7
     - title: Delaware TANF State Plan 2017 - Exhibit 1 and Exhibit 2
       href: https://dhss.delaware.gov/wp-content/uploads/sites/11/dss/pdf/detanfstateplan2017.pdf#page=7
diff --git a/policyengine_us/parameters/gov/states/mo/dss/tanf/minimum_payment.yaml b/policyengine_us/parameters/gov/states/mo/dss/tanf/minimum_payment.yaml
index 758787a62b2..546e356614e 100644
--- a/policyengine_us/parameters/gov/states/mo/dss/tanf/minimum_payment.yaml
+++ b/policyengine_us/parameters/gov/states/mo/dss/tanf/minimum_payment.yaml
@@ -1,7 +1,8 @@
 description: Missouri does not issue TANF payments below this amount.
 
 values:
-  2024-01-01: 10
+  # Rule originated April 22, 1948 with AFDC; carried forward to TANF
+  2002-01-01: 10
 
 metadata:
   unit: currency-USD
diff --git a/policyengine_us/parameters/gov/states/pa/dhs/tanf/income/deductions/work_expense/additional.yaml b/policyengine_us/parameters/gov/states/pa/dhs/tanf/income/deductions/work_expense/additional.yaml
deleted file mode 100644
index 70ba7de905e..00000000000
--- a/policyengine_us/parameters/gov/states/pa/dhs/tanf/income/deductions/work_expense/additional.yaml
+++ /dev/null
@@ -1,15 +0,0 @@
-description: Pennsylvania deducts this additional amount for work expenses under the Temporary Assistance for Needy Families program.
-# Administrative policy effective September 2020. Not codified in PA Code; documented in state plan and handbook.
-
-values:
-  2020-09-26: 200
-
-metadata:
-  unit: currency-USD
-  period: month
-  label: Pennsylvania TANF additional work expense deduction
-  reference:
-    - title: PA DHS TANF State Plan 2024
-      href: https://www.pa.gov/content/dam/copapwp-pagov/en/dhs/documents/services/assistance/documents/tanf/tanf-state-plan-effective-october-1-2024.pdf#page=13
-    - title: PA DHS Cash Assistance Handbook Section 168.22, Work Expense Deduction
-      href: http://services.dpw.state.pa.us/oimpolicymanuals/cash/index.htm#t=160_Income_Deductions%2F160_2_TANF_Earned_Income_Deductions.htm%23160.21_TANF_Earned_Income_Disregard
diff --git a/policyengine_us/parameters/gov/states/pa/dhs/tanf/income/work_expense/deduction.yaml b/policyengine_us/parameters/gov/states/pa/dhs/tanf/income/work_expense/deduction.yaml
new file mode 100644
index 00000000000..46c93b7f746
--- /dev/null
+++ b/policyengine_us/parameters/gov/states/pa/dhs/tanf/income/work_expense/deduction.yaml
@@ -0,0 +1,16 @@
+description: Pennsylvania deducts this amount from countable earned income for work expenses under the Temporary Assistance for Needy Families program.
+# Work Expense Deduction (WED) - applied after 50% earned income disregard
+# Replaced the Work Expense Reimbursement (WER) in September 2020
+
+values:
+  2020-10-01: 200
+
+metadata:
+  unit: currency-USD
+  period: month
+  label: Pennsylvania TANF work expense deduction amount
+  reference:
+    - title: PA DHS TANF State Plan 2024
+      href: https://www.pa.gov/content/dam/copapwp-pagov/en/dhs/documents/services/assistance/documents/tanf/tanf-state-plan-effective-october-1-2024.pdf#page=13
+    - title: PA DHS Cash Assistance Handbook Section 160.22, Work Expense Deduction
+      href: http://services.dpw.state.pa.us/oimpolicymanuals/cash/index.htm#t=160_Income_Deductions%2F160_2_TANF_Earned_Income_Deductions.htm
diff --git a/policyengine_us/parameters/gov/states/pa/dhs/tanf/income/work_expense/reimbursement.yaml b/policyengine_us/parameters/gov/states/pa/dhs/tanf/income/work_expense/reimbursement.yaml
new file mode 100644
index 00000000000..c7ed5455ad3
--- /dev/null
+++ b/policyengine_us/parameters/gov/states/pa/dhs/tanf/income/work_expense/reimbursement.yaml
@@ -0,0 +1,14 @@
+description: Pennsylvania provides this amount as a work expense reimbursement under the Temporary Assistance for Needy Families program.
+# Work Expense Reimbursement (WER) - flat bonus added to TANF grant
+# Active March 2009 to September 2020, then replaced by Work Expense Deduction (WED)
+
+values:
+  2009-04-01: 50
+
+metadata:
+  unit: currency-USD
+  period: month
+  label: Pennsylvania TANF work expense reimbursement amount
+  reference:
+    - title: PA DHS Cash Assistance Handbook Section 137.4, Work Expense Reimbursement
+      href: http://services.dpw.state.pa.us/oimpolicymanuals/cash/137_Cash_Initiatives/137.4_Work_Expense_Reimbursement.htm
diff --git a/policyengine_us/parameters/gov/states/pa/dhs/tanf/income/work_expense/uses_deduction.yaml b/policyengine_us/parameters/gov/states/pa/dhs/tanf/income/work_expense/uses_deduction.yaml
new file mode 100644
index 00000000000..6a2ea22315e
--- /dev/null
+++ b/policyengine_us/parameters/gov/states/pa/dhs/tanf/income/work_expense/uses_deduction.yaml
@@ -0,0 +1,17 @@
+description: Pennsylvania uses a work expense deduction (true) or reimbursement (false) under the Temporary Assistance for Needy Families program.
+# Before 2020: Work Expense Reimbursement (WER) - $50/month added to benefit
+# After 2020: Work Expense Deduction (WED) - $200/month deducted from income
+
+values:
+  2009-04-01: false
+  2020-10-01: true
+
+metadata:
+  unit: bool
+  period: month
+  label: Pennsylvania TANF uses work expense deduction
+  reference:
+    - title: PA DHS Cash Assistance Handbook Section 137.4, Work Expense Reimbursement
+      href: http://services.dpw.state.pa.us/oimpolicymanuals/cash/137_Cash_Initiatives/137.4_Work_Expense_Reimbursement.htm
+    - title: PA DHS TANF State Plan 2024, Work Expense Deduction
+      href: https://www.pa.gov/content/dam/copapwp-pagov/en/dhs/documents/services/assistance/documents/tanf/tanf-state-plan-effective-october-1-2024.pdf#page=13
diff --git a/policyengine_us/parameters/gov/states/ri/dhs/works/income/dependent_care/amount.yaml b/policyengine_us/parameters/gov/states/ri/dhs/works/income/dependent_care/amount.yaml
index fdaaecf3968..4039add258c 100644
--- a/policyengine_us/parameters/gov/states/ri/dhs/works/income/dependent_care/amount.yaml
+++ b/policyengine_us/parameters/gov/states/ri/dhs/works/income/dependent_care/amount.yaml
@@ -9,15 +9,18 @@ metadata:
   reference:
     - title: 218-RICR-20-00-2.15.5(B)(2) Dependent Care Deduction
       href: https://www.law.cornell.edu/regulations/rhode-island/218-RICR-20-00-2.15
+    - title: R.I. Gen. Laws Chapter 40-5.2 - Rhode Island Works Act of 2008
+      href: http://webserver.rilin.state.ri.us/Statutes/TITLE40/40-5.2/INDEX.htm
     - title: Rhode Island Works Program Eligibility
       href: https://dhs.ri.gov/programs-and-services/ri-works-program/eligibility-how-apply
 
 brackets:
+  # Rhode Island Works established July 1, 2008; amounts based on federal SNAP limits
   - threshold:
-      2019-01-01: 0
+      2008-07-01: 0
     amount:
-      2019-01-01: 200
+      2008-07-01: 200
   - threshold:
-      2019-01-01: 2
+      2008-07-01: 2
     amount:
-      2019-01-01: 175
+      2008-07-01: 175
diff --git a/policyengine_us/parameters/gov/states/sd/dss/tanf/payment_standard/max_table_size.yaml b/policyengine_us/parameters/gov/states/sd/dss/tanf/payment_standard/max_table_size.yaml
index 483a8786b77..25a730106bc 100644
--- a/policyengine_us/parameters/gov/states/sd/dss/tanf/payment_standard/max_table_size.yaml
+++ b/policyengine_us/parameters/gov/states/sd/dss/tanf/payment_standard/max_table_size.yaml
@@ -1,12 +1,14 @@
 description: South Dakota uses this amount as the maximum family size in the payment standard table under the Temporary Assistance for Needy Families program.
 
 values:
-  2023-07-01: 12
+  2016-09-01: 12
 
 metadata:
   unit: person
   period: month
   label: South Dakota TANF maximum table family size
   reference:
+    - title: ARSD 67:10:05:03 - Payment Standards (2016)
+      href: https://sdlegislature.gov/api/Rules/Archived/10994.pdf#page=1
     - title: ARSD 67:10:05:03 - Payment Standards
       href: https://sdlegislature.gov/Rules/Administrative/67:10:05:03
diff --git a/policyengine_us/tests/policy/baseline/gov/states/pa/dhs/tanf/income/pa_tanf_earned_income_after_deductions_person.yaml b/policyengine_us/tests/policy/baseline/gov/states/pa/dhs/tanf/income/pa_tanf_earned_income_after_deductions_person.yaml
index f390aa7555d..3f4cad77ca4 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/pa/dhs/tanf/income/pa_tanf_earned_income_after_deductions_person.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/pa/dhs/tanf/income/pa_tanf_earned_income_after_deductions_person.yaml
@@ -79,3 +79,46 @@
     # Step 1: $250 × 50% = $125 (EID: keep 50%)
     # Step 2: $125 - $200 = -$75, clipped to 0 (WED)
     pa_tanf_earned_income_after_deductions_person: 0
+
+# Work Expense Reimbursement (WER) era tests - before Sept 2020
+# In WER era, no $200 WED deduction is applied
+
+- name: Case 8, WER era, low earnings, enrolled recipient, no WED.
+  period: 2019-01
+  input:
+    employment_income_before_lsr: 12_000
+    is_tanf_enrolled: true
+    state_code: PA
+  output:
+    # Monthly: $12,000/12 = $1,000
+    # Step 1: $1,000 × 50% = $500 (EID: keep 50%)
+    # Step 2: No WED in WER era (pre-2020)
+    # Countable: $500
+    pa_tanf_earned_income_after_deductions_person: 500
+
+- name: Case 9, WER era, high earnings, enrolled recipient, no WED.
+  period: 2019-01
+  input:
+    employment_income_before_lsr: 36_000
+    is_tanf_enrolled: true
+    state_code: PA
+  output:
+    # Monthly: $36,000/12 = $3,000
+    # Step 1: $3,000 × 50% = $1,500 (EID: keep 50%)
+    # Step 2: No WED in WER era (pre-2020)
+    # Countable: $1,500
+    pa_tanf_earned_income_after_deductions_person: 1_500
+
+- name: Case 10, WER era, deductions would have zeroed income in WED era.
+  period: 2019-01
+  input:
+    employment_income_before_lsr: 2_400
+    is_tanf_enrolled: true
+    state_code: PA
+  output:
+    # Monthly: $2,400/12 = $200
+    # Step 1: $200 × 50% = $100 (EID: keep 50%)
+    # Step 2: No WED in WER era
+    # In WED era this would be: $100 - $200 = 0
+    # In WER era: $100 (no deduction)
+    pa_tanf_earned_income_after_deductions_person: 100
diff --git a/policyengine_us/tests/policy/baseline/gov/states/pa/dhs/tanf/integration.yaml b/policyengine_us/tests/policy/baseline/gov/states/pa/dhs/tanf/integration.yaml
index 0c77b4b143f..3104d91b042 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/pa/dhs/tanf/integration.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/pa/dhs/tanf/integration.yaml
@@ -384,3 +384,101 @@
     pa_tanf_maximum_benefit: 403
     pa_tanf_countable_income: 550
     pa_tanf: 0
+
+# Work Expense Reimbursement (WER) era integration tests - before Sept 2020
+# WER: $50 bonus added to benefit (not income deduction)
+# WED: $200 deducted from income (not bonus)
+
+- name: Case 14, WER era, family with earned income gets $50 bonus.
+  period: 2019-01
+  input:
+    people:
+      person1:
+        age: 35
+        employment_income_before_lsr: 6_960
+      person2:
+        age: 8
+      person3:
+        age: 5
+    spm_units:
+      spm_unit:
+        members: [person1, person2, person3]
+        is_tanf_enrolled: true
+    households:
+      household:
+        members: [person1, person2, person3]
+        state_code: PA
+  output:
+    # Family of 3: FSA = $403/month (same as 2024)
+    # Person1 monthly: $6,960/12 = $580
+    # WER era: Only 50% EID applied, no $200 WED
+    # $580 × 50% = $290 countable
+    # Base benefit: $403 - $290 = $113
+    # WER bonus: +$50 (family has earned income)
+    # Total benefit: $113 + $50 = $163
+    pa_tanf_maximum_benefit: 403
+    pa_tanf_countable_income: 290
+    pa_tanf: 163
+
+- name: Case 15, WER era vs WED era comparison, same family.
+  period: 2024-01
+  input:
+    people:
+      person1:
+        age: 35
+        employment_income_before_lsr: 6_960
+      person2:
+        age: 8
+      person3:
+        age: 5
+    spm_units:
+      spm_unit:
+        members: [person1, person2, person3]
+        is_tanf_enrolled: true
+    households:
+      household:
+        members: [person1, person2, person3]
+        state_code: PA
+  output:
+    # Same family as Case 14 but in WED era (2024)
+    # Family of 3: FSA = $403/month
+    # Person1 monthly: $6,960/12 = $580
+    # WED era: 50% EID + $200 WED deduction
+    # $580 × 50% = $290; $290 - $200 = $90 countable
+    # Benefit: $403 - $90 = $313
+    # No WER bonus in WED era
+    # WED era benefit ($313) > WER era benefit ($163) by $150
+    pa_tanf_maximum_benefit: 403
+    pa_tanf_countable_income: 90
+    pa_tanf: 313
+
+- name: Case 16, WER era, no earned income, no bonus.
+  period: 2019-01
+  input:
+    people:
+      person1:
+        age: 45
+        employment_income_before_lsr: 0
+        social_security: 2_400
+      person2:
+        age: 10
+      person3:
+        age: 7
+    spm_units:
+      spm_unit:
+        members: [person1, person2, person3]
+    households:
+      household:
+        members: [person1, person2, person3]
+        state_code: PA
+  output:
+    # Family of 3: FSA = $403/month
+    # No earned income, only unearned (SS)
+    # Unearned monthly: $2,400/12 = $200
+    # No EID/WED for unearned income
+    # Countable: $200
+    # Benefit: $403 - $200 = $203
+    # No WER bonus (no earned income)
+    pa_tanf_maximum_benefit: 403
+    pa_tanf_countable_income: 200
+    pa_tanf: 203
diff --git a/policyengine_us/tests/policy/baseline/gov/states/pa/dhs/tanf/pa_tanf.yaml b/policyengine_us/tests/policy/baseline/gov/states/pa/dhs/tanf/pa_tanf.yaml
index ce2ed0f377a..9d40feb12d4 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/pa/dhs/tanf/pa_tanf.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/pa/dhs/tanf/pa_tanf.yaml
@@ -51,3 +51,75 @@
     pa_tanf_eligible: true
   output:
     pa_tanf: 636
+
+# Work Expense Reimbursement (WER) era tests - before Sept 2020
+# WER adds $50 bonus to benefit for families with earned income
+
+- name: Case 7, WER era, family with earned income gets $50 bonus.
+  period: 2019-01
+  input:
+    people:
+      person1:
+        age: 30
+        tanf_gross_earned_income: 500
+    spm_units:
+      spm_unit:
+        members: [person1]
+        pa_tanf_maximum_benefit: 316
+        pa_tanf_countable_income: 100
+        pa_tanf_eligible: true
+    households:
+      household:
+        members: [person1]
+        state_code: PA
+  output:
+    # Base grant: $316 - $100 = $216
+    # WER bonus: $50 (family has earned income)
+    # Total: $216 + $50 = $266
+    pa_tanf: 266
+
+- name: Case 8, WER era, family without earned income, no bonus.
+  period: 2019-01
+  input:
+    people:
+      person1:
+        age: 30
+        tanf_gross_earned_income: 0
+    spm_units:
+      spm_unit:
+        members: [person1]
+        pa_tanf_maximum_benefit: 316
+        pa_tanf_countable_income: 100
+        pa_tanf_eligible: true
+    households:
+      household:
+        members: [person1]
+        state_code: PA
+  output:
+    # Base grant: $316 - $100 = $216
+    # No WER bonus (no earned income)
+    # Total: $216
+    pa_tanf: 216
+
+- name: Case 9, WED era, family with earned income, no bonus.
+  period: 2024-01
+  input:
+    people:
+      person1:
+        age: 30
+        tanf_gross_earned_income: 500
+    spm_units:
+      spm_unit:
+        members: [person1]
+        pa_tanf_maximum_benefit: 316
+        pa_tanf_countable_income: 100
+        pa_tanf_eligible: true
+    households:
+      household:
+        members: [person1]
+        state_code: PA
+  output:
+    # Base grant: $316 - $100 = $216
+    # No WER bonus in WED era (2024)
+    # Total: $216
+    pa_tanf: 216
diff --git a/policyengine_us/variables/gov/states/pa/dhs/tanf/income/pa_tanf_earned_income_after_deductions_person.py b/policyengine_us/variables/gov/states/pa/dhs/tanf/income/pa_tanf_earned_income_after_deductions_person.py
index 1814259ff44..82f22f30b1a 100644
--- a/policyengine_us/variables/gov/states/pa/dhs/tanf/income/pa_tanf_earned_income_after_deductions_person.py
+++ b/policyengine_us/variables/gov/states/pa/dhs/tanf/income/pa_tanf_earned_income_after_deductions_person.py
@@ -14,14 +14,25 @@ class pa_tanf_earned_income_after_deductions_person(Variable):
     )
 
     def formula(person, period, parameters):
-        p = parameters(period).gov.states.pa.dhs.tanf.income.deductions
+        p = parameters(period).gov.states.pa.dhs.tanf.income
 
         gross_earned = person("tanf_gross_earned_income", period)
         disregard_eligible = person.spm_unit(
             "pa_tanf_disregard_eligible", period
         )
 
-        after_eid = gross_earned * (1 - p.earned_income_disregard.percentage)
-        after_wed = max_(after_eid - p.work_expense.additional, 0)
+        # Apply 50% earned income disregard
+        after_eid = gross_earned * (
+            1 - p.deductions.earned_income_disregard.percentage
+        )
+
+        # Apply Work Expense Deduction (WED) only when in effect (post-2020)
+        # Before 2020, Work Expense Reimbursement (WER) was used instead (added to benefit)
+        wed_amount = where(
+            p.work_expense.uses_deduction,
+            p.work_expense.deduction,
+            0,
+        )
+        after_wed = max_(after_eid - wed_amount, 0)
 
         return where(disregard_eligible, after_wed, gross_earned)
diff --git a/policyengine_us/variables/gov/states/pa/dhs/tanf/pa_tanf.py b/policyengine_us/variables/gov/states/pa/dhs/tanf/pa_tanf.py
index 0b00b0aa03a..3ca14aa5904 100644
--- a/policyengine_us/variables/gov/states/pa/dhs/tanf/pa_tanf.py
+++ b/policyengine_us/variables/gov/states/pa/dhs/tanf/pa_tanf.py
@@ -9,11 +9,28 @@ class pa_tanf(Variable):
     definition_period = MONTH
     defined_for = "pa_tanf_eligible"
     reference = (
-        "https://www.pa.gov/agencies/dhs/resources/cash-assistance/tanf"
+        "https://www.pa.gov/agencies/dhs/resources/cash-assistance/tanf",
+        "http://services.dpw.state.pa.us/oimpolicymanuals/cash/137_Cash_Initiatives/137.4_Work_Expense_Reimbursement.htm",
     )
 
     def formula(spm_unit, period, parameters):
+        p = parameters(period).gov.states.pa.dhs.tanf.income.work_expense
+
         maximum_benefit = spm_unit("pa_tanf_maximum_benefit", period)
         countable_income = spm_unit("pa_tanf_countable_income", period)
+        base_grant = max_(maximum_benefit - countable_income, 0)
+
+        # Work Expense Reimbursement (WER): $50/month bonus for families with earned income
+        # Active 2009-2020, before Work Expense Deduction (WED) replaced it
+        gross_earned_income = add(
+            spm_unit, period, ["tanf_gross_earned_income"]
+        )
+        has_earned_income = gross_earned_income > 0
+        uses_wer = p.uses_deduction == False
+        wer_amount = where(
+            uses_wer & has_earned_income,
+            p.reimbursement,
+            0,
+        )
 
-        return max_(maximum_benefit - countable_income, 0)
+        return base_grant + wer_amount