Correct CRFB expanded surtax premium addbacks; isolate salary-reduction reading

changelog.d/hub-crfb-surtax-pretax-premiums-1010.fixed.md

@@ -0,0 +1 @@
+Correct CRFB expanded surtax premium addbacks to use employer-paid coverage and employee pretax premiums without double-counting after-tax employee premiums.

policyengine_us/parameters/gov/contrib/crfb/surtax/increased_base/sources.yaml

@@ -27,8 +27,13 @@ values:
     - foreign_earned_income_exclusion
     # Tax-free bond interest
     - tax_exempt_interest_income
-    # Employer-provided health insurance (premiums)
-    - health_insurance_premiums
+    # Employer-provided health insurance: employer-paid premiums and the
+    # employee's pretax payroll contribution. Including the employee's
+    # pretax contribution is inferred from the broad income definition and
+    # IRS Rev. Rul. 2002-3's treatment of salary-reduction premiums as
+    # employer-provided coverage; after-tax premiums use income in AGI.
+    - employer_sponsored_insurance_premiums
+    - pre_tax_health_insurance_premiums
 
 metadata:
   unit: list
@@ -37,3 +42,5 @@ metadata:
   reference:
     - title: "Committee for a Responsible Federal Budget, Break Glass: A Plan for the Next Economic Shock, footnote 2"
       href: https://www.crfb.org/papers/break-glass-plan-next-economic-shock
+    - title: "IRS Revenue Ruling 2002-3, salary-reduction health insurance premiums #page 1-2"
+      href: https://www.irs.gov/pub/irs-drop/rr-02-3.pdf#page=1

policyengine_us/tests/core/test_dependent_payroll_taxes_ctc_and_surtax_invariants.py

@@ -11,9 +11,9 @@
 expanded base adds amounts to this return's AGI, so it counts the head's and
 spouse's own contributions, exclusions and deductions too.
 
-Each case runs every tax unit twice in one vectorized simulation: once with
-the dependents' amounts as drawn and once with them set to zero. For every
-tax unit:
+Dependent-exclusion cases run every tax unit twice in one vectorized simulation:
+once with the dependents' amounts as drawn and once with them set to zero. For
+every tax unit:
 
 1. A dependent's wages, self-employment income, retirement contributions,
    tax-exempt interest, Social Security benefits and health insurance
@@ -29,6 +29,9 @@
 3. Differential: `ctc_social_security_tax`, the Puerto Rico equivalent,
    `additional_medicare_tax` and the surtax equal an independent numpy
    calculation over the head and spouse.
+4. With AGI held fixed, employer-paid and qualified salary-reduction premiums
+   add the same amount to the surtax base; after-tax premiums add nothing.
+   Generated payment-method cases cover both surtax thresholds.
 
 Invariant 2 leaves out three kinds of dependent amount, which invariant 1
 checks with AGI and its taxable Social Security given as inputs:
@@ -67,12 +70,15 @@
     "traditional_403b_contributions_desired",
     "social_security_dependents",
 ]
-# Dependent amounts that reach the filer's return elsewhere: see the module
-# docstring.
+# Additional dependent amounts checked with AGI held fixed, including all
+# three premium payment methods. Some reach the return elsewhere: see the
+# module docstring.
 OTHER_INPUTS = [
     "self_employment_income",
     "tax_exempt_interest_income",
     "health_insurance_premiums",
+    "employer_sponsored_insurance_premiums",
+    "pre_tax_health_insurance_premiums",
 ]
 PERSON_PAYROLL_TAXES = [
     "employee_social_security_tax",
@@ -85,7 +91,8 @@
     "traditional_403b_contributions",
     "student_loan_interest_ald",
     "tax_exempt_interest_income",
-    "health_insurance_premiums",
+    "employer_sponsored_insurance_premiums",
+    "pre_tax_health_insurance_premiums",
 ]
 
 money = st.integers(0, 60_000).map(float)
@@ -116,6 +123,12 @@ def filer(draw):
         "traditional_401k_contributions_desired": draw(maybe(money)),
         "tax_exempt_interest_income": draw(maybe(money)),
         "health_insurance_premiums": draw(maybe(st.integers(1, 9_000).map(float))),
+        "employer_sponsored_insurance_premiums": draw(
+            maybe(st.integers(1, 9_000).map(float))
+        ),
+        "pre_tax_health_insurance_premiums": draw(
+            maybe(st.integers(1, 9_000).map(float))
+        ),
     }
 
 
@@ -140,6 +153,12 @@ def dependent(draw, *, every_amount):
         person["health_insurance_premiums"] = draw(
             maybe(st.integers(1, 9_000).map(float))
         )
+        person["employer_sponsored_insurance_premiums"] = draw(
+            maybe(st.integers(1, 9_000).map(float))
+        )
+        person["pre_tax_health_insurance_premiums"] = draw(
+            maybe(st.integers(1, 9_000).map(float))
+        )
     return person
 
 
@@ -394,6 +413,82 @@ def test_dependents_amounts_never_change_payroll_taxes_or_surtax_additions(units
     check_every_amount_with_agi_given(units, year)
 
 
+def test_after_tax_premiums_do_not_increase_surtax_with_agi_given():
+    year = 2026
+    unit = {
+        "head": {"age": 40, "health_insurance_premiums": 4_000.0},
+        "spouse": None,
+        "dependents": [{"age": 17, "employment_income": 0.0}],
+        "excess_payroll_tax_withheld": 0.0,
+        "adjusted_gross_income": 150_000.0,
+    }
+    situation, filers, unit_index = build([unit], year)
+    situation["tax_units"]["tax_unit_0"]["filing_status"] = {year: "SINGLE"}
+    simulation = Simulation(situation=situation, tax_benefit_system=surtax_system())
+    # After-tax premiums are already financed from the supplied AGI.
+    # The stale oracle added $4,000 again, incorrectly requiring $540.
+    np.testing.assert_allclose(
+        calculate(simulation, "agi_surtax", year), [500.0], atol=TOLERANCE
+    )
+    assert_surtax_matches_reference(simulation, filers, unit_index, year)
+
+
+@SETTINGS
+@given(
+    amount=st.integers(10, 60_000).map(float),
+    dependent_premiums=st.tuples(
+        st.integers(10, 60_000).map(float),
+        st.integers(10, 60_000).map(float),
+        st.integers(10, 60_000).map(float),
+    ),
+    married=st.booleans(),
+    year=st.sampled_from(YEARS),
+)
+def test_surtax_premium_payment_methods_with_agi_given(
+    amount, dependent_premiums, married, year
+):
+    system = surtax_system()
+    p = system.parameters(year).gov.contrib.crfb.surtax
+    scale = p.rate.joint if married else p.rate.single
+    # Every draw covers a below-threshold base, crossing the first threshold,
+    # the 1% bracket and crossing the top threshold.
+    agi = np.array(
+        [
+            0.0,
+            scale.thresholds[1] - amount / 2,
+            scale.thresholds[1] + amount,
+            scale.thresholds[2] - amount / 2,
+        ]
+    )
+    methods = (
+        "employer_sponsored_insurance_premiums",
+        "pre_tax_health_insurance_premiums",
+        "health_insurance_premiums",
+    )
+    units = [
+        {
+            "head": {"age": 40, method: amount},
+            "spouse": {"age": 40} if married else None,
+            "dependents": [{"age": 17, **dict(zip(methods, dependent_premiums))}],
+            "excess_payroll_tax_withheld": 0.0,
+            "adjusted_gross_income": float(income),
+        }
+        for method in methods
+        for income in agi
+    ]
+    situation, filers, unit_index = build(units, year)
+    simulation = Simulation(situation=situation, tax_benefit_system=system)
+    employer_paid, salary_reduction, after_tax = np.split(
+        calculate(simulation, "agi_surtax", year), 3
+    )
+    np.testing.assert_allclose(employer_paid, salary_reduction, atol=TOLERANCE)
+    # With AGI fixed, switching to after-tax payments lowers the expanded
+    # base by exactly the moved amount. Apply the scale across both brackets.
+    np.testing.assert_allclose(employer_paid, scale.calc(agi + amount), atol=TOLERANCE)
+    np.testing.assert_allclose(after_tax, scale.calc(agi), atol=TOLERANCE)
+    assert_surtax_matches_reference(simulation, filers, unit_index, year)
+
+
 def low_wage_family(married, dependent_wages):
     """Three qualifying children, the EITC barred by interest income and
     wages low enough that payroll taxes decide the refundable CTC."""

policyengine_us/tests/policy/contrib/crfb/agi_surtax.yaml

@@ -18,6 +18,62 @@
   output:
     agi_surtax: 500
 
+- name: Expanded base restores employee pretax premiums and adds employer-paid premiums.
+  period: 2026
+  reforms: policyengine_us.reforms.crfb.agi_surtax.agi_surtax_reform_object
+  input:
+    gov.contrib.crfb.surtax.in_effect: true
+    gov.contrib.crfb.surtax.increased_base.in_effect: true
+    employment_income: 150_000
+    health_insurance_premiums: 4_000
+    pre_tax_health_insurance_premiums: 6_000
+    employer_sponsored_insurance_premiums: 10_000
+    filing_status: SINGLE
+  output:
+    adjusted_gross_income: 144_000
+    # 144,000 AGI + 6,000 pretax + 10,000 employer premiums = 160,000.
+    agi_surtax: 600
+
+- name: Expanded base is unchanged when employee premiums are paid entirely after tax.
+  period: 2026
+  reforms: policyengine_us.reforms.crfb.agi_surtax.agi_surtax_reform_object
+  input:
+    gov.contrib.crfb.surtax.in_effect: true
+    gov.contrib.crfb.surtax.increased_base.in_effect: true
+    employment_income: 150_000
+    health_insurance_premiums: 10_000
+    employer_sponsored_insurance_premiums: 10_000
+    filing_status: SINGLE
+  output:
+    adjusted_gross_income: 150_000
+    # 150,000 AGI + 10,000 employer premiums = the same 160,000 base.
+    agi_surtax: 600
+
+- name: Expanded base does not add after-tax employee premiums to supplied AGI.
+  period: 2026
+  reforms: policyengine_us.reforms.crfb.agi_surtax.agi_surtax_reform_object
+  input:
+    gov.contrib.crfb.surtax.in_effect: true
+    gov.contrib.crfb.surtax.increased_base.in_effect: true
+    adjusted_gross_income: 110_000
+    health_insurance_premiums: 20_000
+    filing_status: SINGLE
+  output:
+    agi_surtax: 100
+
+- name: Expanded base restores pretax employee premiums excluded from supplied AGI.
+  period: 2026
+  reforms: policyengine_us.reforms.crfb.agi_surtax.agi_surtax_reform_object
+  input:
+    gov.contrib.crfb.surtax.in_effect: true
+    gov.contrib.crfb.surtax.increased_base.in_effect: true
+    adjusted_gross_income: 110_000
+    pre_tax_health_insurance_premiums: 20_000
+    filing_status: SINGLE
+  output:
+    agi_surtax: 300
+    income_tax_before_credits: 15_670
+
 - name: Joint couple below threshold
   period: 2026
   reforms: policyengine_us.reforms.crfb.agi_surtax.agi_surtax_reform_object