Apply Savings Credit to people reaching SPA before 2016 (#1126)

* Add 2016 condition

* add changelog

* apply comments

* apply comments

Author: vahid-ahmadi

changelog_entry.yaml

@@ -0,0 +1,4 @@
+- bump: minor
+  changes:
+    fixed:
+    - Implemented 2016 Savings Credit eligibility restriction in Pension Credit.

policyengine_uk/parameters/gov/dwp/pension_credit/savings_credit/cutoff_year.yaml

@@ -0,0 +1,8 @@
+description: People reaching State Pension age after this year are not eligible for Savings Credit.
+metadata:
+  label: Savings Credit eligibility cutoff year
+  reference:
+    - title: State Pension Credit Act 2002
+      href: https://www.legislation.gov.uk/ukpga/2002/16/section/3
+values:
+  2002-01-01: 2016

policyengine_uk/tests/policy/baseline/gov/dwp/pension_credit/savings_credit/is_savings_credit_eligible.yaml

@@ -0,0 +1,70 @@
+- name: No one reached SPA before the cutoff year, ineligible for savings credit
+  period: 2023
+  input:
+    people:
+      person:
+        age: 68
+        is_male: true
+        state_pension_age: 66
+    benunits:
+      benunit:
+        members: [person]
+        savings_credit_income: 10000
+  output:
+    is_savings_credit_eligible: false
+
+- name: Has pre-cutoff year SPA member and income above threshold (single), eligible
+  period: 2023
+  input:
+    people:
+      person:
+        age: 78
+        is_male: false
+        state_pension_age: 60
+    benunits:
+      benunit:
+        members: [person]
+        relation_type: SINGLE
+        savings_credit_income: 10200
+  output:
+    is_savings_credit_eligible: true
+
+- name: One member reached SPA before cutoff year and income above threshold (couple), eligible
+  period: 2023
+  input:
+    people:
+      person:
+        age: 73
+        is_male: true
+        state_pension_age: 65
+      spouse:
+        age: 66
+        is_male: false
+        state_pension_age: 66
+    benunits:
+      benunit:
+        members: [person, spouse]
+        relation_type: COUPLE
+        savings_credit_income: 16000
+  output:
+    is_savings_credit_eligible: true
+
+- name: No pre-cutoff year SPA member and income above threshold (couple), ineligible
+  period: 2023
+  input:
+    people:
+      person:
+        age: 67
+        is_male: true
+        state_pension_age: 66
+      spouse:
+        age: 65
+        is_male: false
+        state_pension_age: 66
+    benunits:
+      benunit:
+        members: [person, spouse]
+        relation_type: COUPLE
+        savings_credit_income: 16000
+  output:
+    is_savings_credit_eligible: false

policyengine_uk/tests/policy/baseline/gov/dwp/pension_credit/savings_credit/meets_savings_credit_age_requirement.yaml

@@ -0,0 +1,77 @@
+- name: Person born in 1948 reaches SPA before cutoff year
+  period: 2023
+  input:
+    people:
+      person:
+        age: 75  # Born in 1948, reached SPA around 2013-2014
+        state_pension_age: 65
+    benunits:
+      benunit:
+        members: [person]
+  output:
+    meets_savings_credit_age_requirement: true
+
+- name: Person born in 1952 reaches SPA before cutoff year
+  period: 2023
+  input:
+    people:
+      person:
+        age: 71  # Born in 1952, reached SPA around 2015
+        state_pension_age: 63
+    benunits:
+      benunit:
+        members: [person]
+  output:
+    meets_savings_credit_age_requirement: true
+
+- name: Person born in 1954 reaches SPA after cutoff year
+  period: 2023
+  input:
+    people:
+      person:
+        age: 69  # Born in 1954, reached SPA around 2017-2018
+        state_pension_age: 63.5
+    benunits:
+      benunit:
+        members: [person]
+  output:
+    meets_savings_credit_age_requirement: false
+
+- name: Person born in 1960 reaches SPA after cutoff year
+  period: 2023
+  input:
+    people:
+      person:
+        age: 63  # Born in 1960, will reach SPA around 2026-2027
+        state_pension_age: 66
+    benunits:
+      benunit:
+        members: [person]
+  output:
+    meets_savings_credit_age_requirement: false
+
+- name: Test in 2015 - Person born in 1950 reaches SPA before cutoff year
+  period: 2015
+  input:
+    people:
+      person:
+        age: 65  # Born in 1950, reached SPA around 2013
+        state_pension_age: 63
+    benunits:
+      benunit:
+        members: [person]
+  output:
+    meets_savings_credit_age_requirement: true
+
+- name: Test in 2017 - Person who reached SPA in 2015 is eligible
+  period: 2017
+  input:
+    people:
+      person:
+        age: 65  # Born in 1952, reached SPA in 2015
+        state_pension_age: 63
+    benunits:
+      benunit:
+        members: [person]
+  output:
+    meets_savings_credit_age_requirement: true

policyengine_uk/variables/gov/dwp/pension_credit/savings_credit/is_savings_credit_eligible.py

@@ -10,8 +10,13 @@ class is_savings_credit_eligible(Variable):
     reference = "https://www.legislation.gov.uk/ukpga/2002/16/section/3"
 
     def formula(benunit, period, parameters):
+        # Check if any member reached SPA before the cutoff year
+        has_pre_cutoff_spa_member = benunit.any(
+            benunit.members("meets_savings_credit_age_requirement", period)
+        )
         income = benunit("savings_credit_income", period)
         sc = parameters(period).gov.dwp.pension_credit.savings_credit
         relation_type = benunit("relation_type", period)
         threshold = sc.threshold[relation_type]
-        return income >= threshold
+        meets_income_threshold = income >= threshold
+        return has_pre_cutoff_spa_member & meets_income_threshold

policyengine_uk/variables/gov/dwp/pension_credit/savings_credit/meets_savings_credit_age_requirement.py

@@ -0,0 +1,22 @@
+from policyengine_uk.model_api import *
+
+
+class meets_savings_credit_age_requirement(Variable):
+    value_type = bool
+    entity = Person
+    label = "whether the person reached State Pension Age before the Savings Credit cutoff year"
+    definition_period = YEAR
+
+    def formula(person, period, parameters):
+        # https://www.legislation.gov.uk/ukpga/2002/16/section/3
+        p = parameters(period).gov.dwp.pension_credit.savings_credit
+        current_age = person("age", period)
+        # State pension age
+        spa = person("state_pension_age", period)
+        # The year we're evaluating
+        evaluation_year = period.start.year
+        # Calculate what year the person reached/will reach SPA
+        birth_year = evaluation_year - current_age
+        spa_year = birth_year + spa
+        # Get the cutoff year from parameters
+        return spa_year < p.cutoff_year