Remove pass-through allowance variables (#414) (#1640)

* Remove pass-through allowance variables (#414)

`trading_allowance`, `property_allowance`, and `dividend_allowance`
variables each just returned their same-named parameter. Callers
(`trading_allowance_deduction`, `property_allowance_deduction`,
`taxable_property_income`, `taxed_dividend_income`) now read the
parameter directly.

The `taxable_self_employment_income` deductions list now references
`trading_allowance_deduction` (the capped amount actually deductible
against self-employment income) instead of the raw allowance. This
gives identical taxable-income outputs since the pre-existing
`max_(0, ...)` clamp already absorbed any over-deduction.

Tests that previously injected these variables as inputs now override
the corresponding parameter path. The obsolete test that asserted the
default `dividend_allowance` value is dropped since the variable no
longer exists.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* Use allowance deduction variables in taxable income

* Format carbon tax notebook

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-authored-by: Max Ghenis <mghenis@gmail.com>

Author: 3 people

changelog.d/414.md

@@ -0,0 +1 @@
+- Remove `trading_allowance`, `property_allowance`, and `dividend_allowance` variables that were pure pass-throughs around their same-named parameters. Callers now read the parameter directly, and the `taxable_self_employment_income` deductions list references `trading_allowance_deduction` (the capped amount actually deductible against self-employment income) rather than the raw allowance.

docs/book/programs/contrib/ubi-center/carbon-tax.ipynb

@@ -978,7 +978,7 @@
     "    yaxis_title=None,\n",
     "    width=800,\n",
     "    height=600,\n",
-    ")\n"
+    ")"
    ]
   }
  ],

policyengine_uk/parameters/gov/hmrc/income_tax/bases/taxable_self_employment_income_deductions.yaml

@@ -3,7 +3,7 @@ values:
   0000-01-01:
     - loss_relief
     - capital_allowances
-    - trading_allowance
+    - trading_allowance_deduction
 metadata:
   unit: list
   label: Deductions from self-employment income

policyengine_uk/tests/policy/baseline/gov/hmrc/income_tax/allowances/is_allowance_eligible.yaml

@@ -39,32 +39,26 @@
 - name: Trading Allowance Deduction
   period: 2024
   input:
-    trading_allowance: 2000
+    gov.hmrc.income_tax.allowances.trading_allowance: 2000
     self_employment_income: 1500
-  output: 
+  output:
     trading_allowance_deduction: 1500.0
 
 - name: Property Allowance Deduction
   period: 2024
   input:
     property_income: 3000
-    property_allowance: 1000
-  output: 
+    gov.hmrc.income_tax.allowances.property_allowance: 1000
+  output:
     property_allowance_deduction: 1000.0
 
 - name: Savings Allowance
   period: 2024
   input:
     tax_band: STARTER
-  output: 
+  output:
     savings_allowance: 1000.0
 
-- name: Dividend Allowance
-  period: 2024
-  input: {}
-  output: 
-    dividend_allowance: 500.0
-
 - name: Allowances Applicable to Adjusted Net Income
   period: 2024
   input:

policyengine_uk/tests/policy/baseline/gov/hmrc/income_tax/bases/taxable_property_income.yaml

@@ -2,70 +2,78 @@
   period: 2024
   input:
     property_income: 0
-    property_allowance: 0
+    gov.hmrc.income_tax.allowances.property_allowance: 0
   output:
     taxable_property_income: 0
 
 - name: Property income fully covered by allowance
   period: 2024
   input:
     property_income: 1000
-    property_allowance: 1000
+    gov.hmrc.income_tax.allowances.property_allowance: 1000
   output:
     taxable_property_income: 0
 
 - name: Property income partially taxable
   period: 2024
   input:
     property_income: 10000
-    property_allowance: 1000
+    gov.hmrc.income_tax.allowances.property_allowance: 1000
   output:
     taxable_property_income: 9000
 
 - name: High property income with standard allowance
   period: 2024
   input:
     property_income: 50000
-    property_allowance: 1000
+    gov.hmrc.income_tax.allowances.property_allowance: 1000
   output:
     taxable_property_income: 49000
 
 - name: Property income with no allowance
   period: 2024
   input:
     property_income: 5000
-    property_allowance: 0
+    gov.hmrc.income_tax.allowances.property_allowance: 0
   output:
     taxable_property_income: 5000
 
 - name: Very low positive property income
   period: 2024
   input:
     property_income: 1
-    property_allowance: 0
+    gov.hmrc.income_tax.allowances.property_allowance: 0
   output:
     taxable_property_income: 1
 
 - name: Property allowance exceeds income
   period: 2024
   input:
     property_income: 500
-    property_allowance: 1000
+    gov.hmrc.income_tax.allowances.property_allowance: 1000
   output:
     taxable_property_income: 0
 
 - name: High values for both income and allowance
   period: 2024
   input:
     property_income: 100000
-    property_allowance: 50000
+    gov.hmrc.income_tax.allowances.property_allowance: 50000
   output:
     taxable_property_income: 50000
 
 - name: Decimal values
   period: 2024
   input:
     property_income: 1234.56
-    property_allowance: 1000.00
+    gov.hmrc.income_tax.allowances.property_allowance: 1000.00
   output:
-    taxable_property_income: 234.56
+    taxable_property_income: 234.56
+
+- name: Pre-net property income can override allowance deduction
+  period: 2024
+  input:
+    property_income: 1234.56
+    property_allowance_deduction: 0
+  output:
+    taxable_property_income: 1234.56

policyengine_uk/tests/policy/baseline/gov/hmrc/income_tax/bases/taxable_self_employment_income.yaml

@@ -31,7 +31,7 @@
     self_employment_income: 0
     loss_relief: 0
     capital_allowances: 0
-    trading_allowance: 0
+    gov.hmrc.income_tax.allowances.trading_allowance: 0
   output:
     taxable_self_employment_income: 0
 
@@ -41,7 +41,7 @@
     self_employment_income: 50000
     loss_relief: 0
     capital_allowances: 0
-    trading_allowance: 0
+    gov.hmrc.income_tax.allowances.trading_allowance: 0
   output:
     taxable_self_employment_income: 50000
 
@@ -51,7 +51,7 @@
     self_employment_income: 30000
     loss_relief: 10000
     capital_allowances: 15000
-    trading_allowance: 5000
+    gov.hmrc.income_tax.allowances.trading_allowance: 5000
   output:
     taxable_self_employment_income: 0
 
@@ -61,7 +61,7 @@
     self_employment_income: 50000
     loss_relief: 5000
     capital_allowances: 10000
-    trading_allowance: 1000
+    gov.hmrc.income_tax.allowances.trading_allowance: 1000
   output:
     taxable_self_employment_income: 34000
 
@@ -71,7 +71,7 @@
     self_employment_income: 200000
     loss_relief: 20000
     capital_allowances: 30000
-    trading_allowance: 1000
+    gov.hmrc.income_tax.allowances.trading_allowance: 1000
   output:
     taxable_self_employment_income: 149000
 
@@ -81,7 +81,7 @@
     self_employment_income: 1000
     loss_relief: 100
     capital_allowances: 200
-    trading_allowance: 300
+    gov.hmrc.income_tax.allowances.trading_allowance: 300
   output:
     taxable_self_employment_income: 400
 
@@ -91,7 +91,7 @@
     self_employment_income: 50000
     loss_relief: 30000
     capital_allowances: 25000
-    trading_allowance: 1000
+    gov.hmrc.income_tax.allowances.trading_allowance: 1000
   output:
     taxable_self_employment_income: 0
 
@@ -101,7 +101,7 @@
     self_employment_income: 1000000
     loss_relief: 200000
     capital_allowances: 300000
-    trading_allowance: 1000
+    gov.hmrc.income_tax.allowances.trading_allowance: 1000
   output:
     taxable_self_employment_income: 499000
 
@@ -111,6 +111,16 @@
     self_employment_income: 50000.50
     loss_relief: 10000.25
     capital_allowances: 5000.75
-    trading_allowance: 1000.00
+    gov.hmrc.income_tax.allowances.trading_allowance: 1000.00
   output:
-    taxable_self_employment_income: 33999.50
+    taxable_self_employment_income: 33999.50
+
+- name: Pre-net self-employment income can override trading allowance deduction
+  period: 2024
+  input:
+    self_employment_income: 1234.56
+    loss_relief: 0
+    capital_allowances: 0
+    trading_allowance_deduction: 0
+  output:
+    taxable_self_employment_income: 1234.56

policyengine_uk/tests/policy/baseline/gov/hmrc/income_tax/bases/taxed_dividend_income.yaml

@@ -2,7 +2,7 @@
   period: 2024
   input:
     taxable_dividend_income: 0
-    dividend_allowance: 1000
+    gov.hmrc.income_tax.allowances.dividend_allowance: 1000
     # Nullify Personal Allowance for testing purposes
     gov.hmrc.income_tax.allowances.personal_allowance.amount: 0
   output:
@@ -12,7 +12,7 @@
   period: 2024
   input:
     taxable_dividend_income: 500
-    dividend_allowance: 1000
+    gov.hmrc.income_tax.allowances.dividend_allowance: 1000
     # Nullify Personal Allowance for testing purposes
     gov.hmrc.income_tax.allowances.personal_allowance.amount: 0
   output:
@@ -22,7 +22,7 @@
   period: 2024
   input:
     taxable_dividend_income: 1000
-    dividend_allowance: 1000
+    gov.hmrc.income_tax.allowances.dividend_allowance: 1000
     # Nullify Personal Allowance for testing purposes
     gov.hmrc.income_tax.allowances.personal_allowance.amount: 0
   output:
@@ -32,7 +32,7 @@
   period: 2024
   input:
     taxable_dividend_income: 1100
-    dividend_allowance: 1000
+    gov.hmrc.income_tax.allowances.dividend_allowance: 1000
     # Nullify Personal Allowance for testing purposes
     gov.hmrc.income_tax.allowances.personal_allowance.amount: 0
   output:
@@ -42,7 +42,7 @@
   period: 2024
   input:
     taxable_dividend_income: 50000
-    dividend_allowance: 2000
+    gov.hmrc.income_tax.allowances.dividend_allowance: 2000
     # Nullify Personal Allowance for testing purposes
     gov.hmrc.income_tax.allowances.personal_allowance.amount: 0
   output:
@@ -52,7 +52,7 @@
   period: 2024
   input:
     taxable_dividend_income: 1000000
-    dividend_allowance: 2000
+    gov.hmrc.income_tax.allowances.dividend_allowance: 2000
     # Nullify Personal Allowance for testing purposes
     gov.hmrc.income_tax.allowances.personal_allowance.amount: 0
   output:
@@ -62,7 +62,7 @@
   period: 2024
   input:
     taxable_dividend_income: 5000
-    dividend_allowance: 0
+    gov.hmrc.income_tax.allowances.dividend_allowance: 0
     # Nullify Personal Allowance for testing purposes
     gov.hmrc.income_tax.allowances.personal_allowance.amount: 0
   output:
@@ -72,7 +72,7 @@
   period: 2024
   input:
     taxable_dividend_income: 2500.50
-    dividend_allowance: 2000.00
+    gov.hmrc.income_tax.allowances.dividend_allowance: 2000.00
     # Nullify Personal Allowance for testing purposes
     gov.hmrc.income_tax.allowances.personal_allowance.amount: 0
   output:
@@ -82,7 +82,7 @@
   period: 2024
   input:
     taxable_dividend_income: 1000
-    dividend_allowance: 2000
+    gov.hmrc.income_tax.allowances.dividend_allowance: 2000
     # Nullify Personal Allowance for testing purposes
     gov.hmrc.income_tax.allowances.personal_allowance.amount: 0
   output:
@@ -92,7 +92,7 @@
   period: 2024
   input:
     taxable_dividend_income: 1000.01
-    dividend_allowance: 1000
+    gov.hmrc.income_tax.allowances.dividend_allowance: 1000
     # Nullify Personal Allowance for testing purposes
     gov.hmrc.income_tax.allowances.personal_allowance.amount: 0
   output:

policyengine_uk/variables/gov/hmrc/income_tax/allowances/dividend_allowance.py

@@ -10,7 +10,10 @@ class property_allowance_deduction(Variable):
     unit = GBP
 
     def formula(person, period, parameters):
+        property_allowance = parameters(
+            period
+        ).gov.hmrc.income_tax.allowances.property_allowance
         return min_(
             person("property_income", period),
-            person("property_allowance", period),
+            property_allowance,
         )