Add annual additions retirement limit parameter

policyengine_us/parameters/gov/irs/gross_income/retirement_contributions/limit/401k.yaml

@@ -7,6 +7,7 @@ values:
   2023-01-01: 22_500
   2024-01-01: 23_000
   2025-01-01: 23_500
+  2026-01-01: 24_500
 metadata:
   unit: currency-USD
   period: year
@@ -22,4 +23,3 @@ metadata:
   # Inflation adjusted amounts
   - title: Cost-of-Living Adjustments for Retirement Items
     href: https://www.irs.gov/pub/irs-tege/cola-table.pdf#page=1
-

policyengine_us/parameters/gov/irs/gross_income/retirement_contributions/limit/annual_additions.yaml

@@ -0,0 +1,25 @@
+description: The US limits annual additions to a defined contribution plan to this amount.
+values:
+  2018-01-01: 55_000
+  2019-01-01: 56_000
+  2020-01-01: 57_000
+  2021-01-01: 58_000
+  2022-01-01: 61_000
+  2023-01-01: 66_000
+  2024-01-01: 69_000
+  2025-01-01: 70_000
+  2026-01-01: 72_000
+metadata:
+  unit: currency-USD
+  period: year
+  label: defined contribution annual additions limit
+  uprating:
+    parameter: gov.irs.uprating
+    rounding:
+      type: downwards
+      interval: 1000
+  references:
+  - title: 26 U.S. Code § 415 - Limitations on benefits and contributions under qualified plans
+    href: https://www.law.cornell.edu/uscode/text/26/415
+  - title: Cost-of-Living Adjustments for Retirement Items
+    href: https://www.irs.gov/pub/irs-tege/cola-table.pdf#page=1

policyengine_us/tests/policy/baseline/parameters/test_uprating_extensions.py

@@ -104,3 +104,25 @@ def test_cpi_relationships():
         # Just verify both exist and are positive
         assert cpi_u > 0, f"CPI-U should be positive in {year}"
         assert c_cpi_u > 0, f"Chained CPI-U should be positive in {year}"
+
+
+def test_retirement_contribution_limits_include_latest_explicit_irs_values():
+    """Retirement contribution parameters should reflect the latest published IRS anchors."""
+    from policyengine_us import Microsimulation
+
+    sim = Microsimulation()
+
+    p2025 = sim.tax_benefit_system.parameters("2025-01-01")
+    p2026 = sim.tax_benefit_system.parameters("2026-01-01")
+    p2027 = sim.tax_benefit_system.parameters("2027-01-01")
+
+    limits2025 = p2025.gov.irs.gross_income.retirement_contributions.limit
+    limits2026 = p2026.gov.irs.gross_income.retirement_contributions.limit
+    limits2027 = p2027.gov.irs.gross_income.retirement_contributions.limit
+
+    assert limits2025["401k"] == 23_500
+    assert limits2026["401k"] == 24_500
+    assert limits2026.annual_additions == 72_000
+
+    assert limits2027["401k"] >= limits2026["401k"]
+    assert limits2027.annual_additions >= limits2026.annual_additions