From f011f5fd0b2feef9a61b4762c47a17a53f29ee55 Mon Sep 17 00:00:00 2001
From: Sam Brown <sam@sgb.io>
Date: Wed, 27 Sep 2023 19:24:50 +0100
Subject: [PATCH] Return zero taxes instead of throwing when income is below PA
 (#9)

---
 src/incomeTax.test.ts | 2 ++
 src/incomeTax.ts      | 7 ++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/incomeTax.test.ts b/src/incomeTax.test.ts
index dde7d6c..8571a6a 100644
--- a/src/incomeTax.test.ts
+++ b/src/incomeTax.test.ts
@@ -2,6 +2,8 @@ import { calculateIncomeTax } from "./incomeTax";
 import { calculatePersonalAllowance } from "./personalAllowance";
 
 const expectations = [
+  { taxableAnnualIncome: 0, basic: 0, higher: 0, additional: 0 },
+  { taxableAnnualIncome: 5_000, basic: 0, higher: 0, additional: 0 },
   { taxableAnnualIncome: 15_000, basic: 486, higher: 0, additional: 0 },
   { taxableAnnualIncome: 17_500, basic: 986, higher: 0, additional: 0 },
   { taxableAnnualIncome: 20_000, basic: 1486, higher: 0, additional: 0 },
diff --git a/src/incomeTax.ts b/src/incomeTax.ts
index b7357d0..bda2b8e 100644
--- a/src/incomeTax.ts
+++ b/src/incomeTax.ts
@@ -85,5 +85,10 @@ export const calculateIncomeTax = ({
     };
   }
 
-  throw new Error("Unexpected Input");
+  // Income is lower than the personal allowance - no income tax
+  return {
+    basicRateTax: 0,
+    higherRateTax: 0,
+    additionalRateTax: 0,
+  };
 };