Keep a filer who can be claimed as a dependent out of the premium tax credit family, and apply each state premium program's rule

changelog.d/claimable-filer-ptc.fixed.md

@@ -0,0 +1 @@
+Apply IRC 36B(c)(1)(D) to the premium tax credit: a filer who can be claimed as a dependent on another return is outside the tax family (26 CFR 1.36B-1(d)(2)), so the credit uses the tax family size for the poverty line and the coverage family's benchmark premium, on a joint return the other spouse keeps the credit, and the Washington, Massachusetts, Connecticut, Colorado, Maryland, California, New Mexico, Vermont and New Jersey premium programs follow their own rules for that person.

policyengine_us/reforms/aca/aca_ptc_700_fpl_cliff.py

@@ -66,7 +66,16 @@ def formula(person, period, parameters):
             )
             is_income_eligible = standard_income_eligible | below_fpl_exception
 
-            return person("pays_aca_premium", period) & ~separate & is_income_eligible
+            # The reform leaves 26 U.S.C. 36B(c)(1)(D) in place: someone
+            # another taxpayer can claim is outside the tax family.
+            tax_family_member = person("is_aca_tax_family_member", period)
+
+            return (
+                person("pays_aca_premium", period)
+                & tax_family_member
+                & ~separate
+                & is_income_eligible
+            )
 
     class reform(Reform):
         def apply(self):

policyengine_us/reforms/aca/aca_ptc_additional_bracket.py

@@ -73,11 +73,16 @@ def formula(person, period, parameters):
             child_pays = person("aca_child_index", period) <= p_aca.max_child_count
             pays_aca_premium = is_aca_adult | child_pays
 
+            # The reform leaves 26 U.S.C. 36B(c)(1)(D) in place: someone
+            # another taxpayer can claim is outside the tax family.
+            tax_family_member = person("is_aca_tax_family_member", period)
+
             return (
                 is_status_eligible
                 & is_coverage_eligible
                 & is_income_eligible
                 & pays_aca_premium
+                & tax_family_member
             )
 
     class reform(Reform):

policyengine_us/reforms/aca/aca_ptc_simplified_bracket.py

@@ -74,11 +74,16 @@ def formula(person, period, parameters):
             child_pays = person("aca_child_index", period) <= p_aca.max_child_count
             pays_aca_premium = is_aca_adult | child_pays
 
+            # The reform leaves 26 U.S.C. 36B(c)(1)(D) in place: someone
+            # another taxpayer can claim is outside the tax family.
+            tax_family_member = person("is_aca_tax_family_member", period)
+
             return (
                 is_status_eligible
                 & is_coverage_eligible
                 & is_income_eligible
                 & pays_aca_premium
+                & tax_family_member
             )
 
     class reform(Reform):