HMA-9175 Fixed negative taxable income to default 0 when yearly income is less than tax free amount.

CHANGELOG.md

@@ -5,6 +5,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
+- Fixed negative taxable income to default 0 when income is less than tax free amount.
 - Fixed default tax code comparison when Tapering not applied and yearly income above 100k.
 
 ## [2.14.1] - 2024-10-15Z

src/commonMain/kotlin/uk/gov/hmrc/calculator/Calculator.kt

@@ -121,9 +121,11 @@ class Calculator @JvmOverloads constructor(
         val studentLoan = StudentLoanCalculation(taxYear, yearlyWages, studentLoanPlans)
         studentLoan.studentLoanClarification?.let { listOfClarification.add(it) }
 
-        val taxableIncome = amountToAddToWages?.let { kCodeAdjustedAmount ->
-            (yearlyWageAfterPension - taxFreeAmount) + kCodeAdjustedAmount
-        } ?: (yearlyWageAfterPension - taxFreeAmount)
+        val taxableIncome = (
+            amountToAddToWages?.let { kCodeAdjustedAmount ->
+                (yearlyWageAfterPension - taxFreeAmount) + kCodeAdjustedAmount
+            } ?: (yearlyWageAfterPension - taxFreeAmount)
+            ).coerceAtLeast(ZERO)
 
         return createResponse(
             taxCodeType,
@@ -414,4 +416,8 @@ class Calculator @JvmOverloads constructor(
         val method: PensionMethod,
         val contributionAmount: Double,
     )
+
+    private companion object {
+        const val ZERO = 0.0
+    }
 }

src/commonTest/kotlin/uk/gov/hmrc/calculator/CalculatorTests.kt

@@ -36,6 +36,38 @@ import kotlin.test.assertTrue
 
 internal class CalculatorTests {
 
+    @Test
+    fun `GIVEN TWENTY_TWENTY_FOUR WHEN wage is less than personal allowance THEN calculates response`() {
+        val result = Calculator(
+            taxCode = "1257L",
+            userSuppliedTaxCode = false,
+            wages = 7000.0,
+            payPeriod = PayPeriod.YEARLY,
+            taxYear = TaxYear.TWENTY_TWENTY_FOUR
+        ).run()
+        Logger.i(result.prettyPrintDataClass())
+
+        assertEquals(Country.ENGLAND, result.country)
+        assertFalse(result.isKCode)
+
+        val yearly = result.yearly
+        assertEquals(PayPeriod.YEARLY, yearly.payPeriod)
+        assertEquals(ZERO, yearly.employeesNI)
+        assertEquals(ZERO, yearly.employersNI)
+        assertEquals(7000.00, yearly.wages)
+        assertEquals(12570.0, yearly.taxFree)
+        assertEquals(ZERO, yearly.taxToPay)
+        assertEquals(7000.0, yearly.takeHome)
+        assertEquals(ZERO, yearly.pensionContribution)
+        assertEquals(7000.0, yearly.wageAfterPensionDeduction)
+        assertEquals(ZERO, yearly.taperingAmountDeduction)
+        assertNull(yearly.studentLoanBreakdown)
+        assertEquals(ZERO, yearly.finalStudentLoanAmount)
+        assertEquals(ZERO, yearly.finalPostgraduateLoanAmount)
+        assertEquals(ZERO, yearly.otherAmount)
+        assertEquals(ZERO, yearly.taxableIncome)
+    }
+
     @Test
     fun `GIVEN TWENTY_TWENTY_ONE WHEN 40000 wage THEN calculates response`() {
         val result = Calculator(
@@ -1957,4 +1989,8 @@ internal class CalculatorTests {
 
         assertEquals(listOfExpectedResult, result.listOfClarification)
     }
+
+    private companion object {
+        const val ZERO = 0.0
+    }
 }