Exclude high-value council tax surcharge under abolish_council_tax (#1670) (#1693)

The surcharge is defined on top of council tax bands, so when council tax is
abolished it should drop out of household_tax and gov_tax alongside the
council_tax line. Filter both aggregates accordingly and add a YAML case.

Author: vahid-ahmadi

changelog.d/1670.md

@@ -0,0 +1 @@
+- Exclude `high_value_council_tax_surcharge` from `household_tax` and `gov_tax` when `gov.contrib.abolish_council_tax` is in force, since the surcharge is defined on top of council tax bands.

policyengine_uk/tests/policy/baseline/gov/hmrc/council_tax/high_value_council_tax_surcharge.yaml

@@ -49,3 +49,17 @@
     high_value_council_tax_surcharge: 0
     household_tax: 0
     gov_tax: 0
+- name: Abolishing council tax also drops the high-value surcharge from aggregates
+  period: 2028
+  input:
+    gov.contrib.abolish_council_tax: true
+    region: LONDON
+    main_residence_value: 2_554_326.811538164
+    main_residential_property_purchased: 0
+    council_tax: 1_500
+    household_owns_tv: false
+    gov.hmrc.stamp_duty.property_sale_rate: 0
+  output:
+    high_value_council_tax_surcharge: 2_500
+    household_tax: 0
+    gov_tax: 0

policyengine_uk/variables/gov/gov_tax.py

@@ -41,7 +41,9 @@ def formula(household, period, parameters):
         abolish_council_tax = parameters.gov.contrib.abolish_council_tax(period)
         if abolish_council_tax:
             variables = [
-                variable for variable in variables if variable != "council_tax"
+                variable
+                for variable in variables
+                if variable not in ["council_tax", "high_value_council_tax_surcharge"]
             ]
 
         return add(household, period, variables)

policyengine_uk/variables/gov/hmrc/household_tax.py

@@ -43,7 +43,11 @@ def formula(household, period, parameters):
             return add(
                 household,
                 period,
-                [tax for tax in HOUSEHOLD_TAX_VARIABLES if tax not in ["council_tax"]],
+                [
+                    tax
+                    for tax in HOUSEHOLD_TAX_VARIABLES
+                    if tax not in ["council_tax", "high_value_council_tax_surcharge"]
+                ],
             )
         else:
             return add(household, period, HOUSEHOLD_TAX_VARIABLES)