Make 2024/25 the default, add tests (#19)

README.md

@@ -11,8 +11,8 @@ This library makes it easy to calculate, based on a PAYE taxable salary:
 
 Multiple versions of the HMRC rates can be supported, although only the follwing years have been implemented:
 
-- 2024/25
-- 2023/24 (default)
+- 2024/25 (default)
+- 2023/24
 - 2022/23
 
 Works in all modern browsers and Node.js (LTS recommended).

src/hmrc.test.ts

@@ -1,8 +1,10 @@
 import { getHmrcRates } from "./hmrc";
 
 describe("getHmrcRates", () => {
-  test("It uses default 2023/24 rates", () => {
-    expect(getHmrcRates().DEFAULT_PERSONAL_ALLOWANCE).toEqual(12570);
+  test("It uses default 2024/25 rates", () => {
+    const rates = getHmrcRates();
+    expect(rates.DEFAULT_PERSONAL_ALLOWANCE).toEqual(12570);
+    expect(rates.NI_MIDDLE_RATE).toEqual(0.08);
   });
 
   test("It uses explicit 2022/23 rates", () => {
@@ -12,4 +14,8 @@ describe("getHmrcRates", () => {
   test("It uses explicit 2023/24 rates", () => {
     expect(getHmrcRates("2023/24").DEFAULT_PERSONAL_ALLOWANCE).toEqual(12570);
   });
+
+  test("It uses explicit 2024/25 rates", () => {
+    expect(getHmrcRates("2024/25").DEFAULT_PERSONAL_ALLOWANCE).toEqual(12570);
+  });
 });

src/hmrc.ts

@@ -106,7 +106,7 @@ const taxRates: Record<TaxYear, TaxRates> = {
 
 export const getHmrcRates = (taxYear?: TaxYear) => {
   if (!taxYear) {
-    return taxRates["2023/24"];
+    return taxRates["2024/25"];
   }
 
   return taxRates[taxYear];

src/incomeTax.test.ts

@@ -1,7 +1,7 @@
 import { calculateIncomeTax } from "./incomeTax";
 import { calculatePersonalAllowance } from "./personalAllowance";
 
-const expectations = [
+const expectationsA = [
   { 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 },
@@ -66,8 +66,8 @@ const expectations = [
   },
 ];
 
-describe("calculateIncomeTax", () => {
-  expectations.forEach((expectation) => {
+describe("calculateIncomeTax (23/24)", () => {
+  expectationsA.forEach((expectation) => {
     const { taxableAnnualIncome, basic, higher, additional } = expectation;
     test(taxableAnnualIncome.toString(), () => {
       const personalAllowance = calculatePersonalAllowance({
@@ -87,3 +87,90 @@ describe("calculateIncomeTax", () => {
     });
   });
 });
+
+const expectationsB = [
+  { 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 },
+  { taxableAnnualIncome: 22_500, basic: 1986, higher: 0, additional: 0 },
+  { taxableAnnualIncome: 25_000, basic: 2486, higher: 0, additional: 0 },
+  { taxableAnnualIncome: 50_000, basic: 7486, higher: 0, additional: 0 },
+  { taxableAnnualIncome: 55_000, basic: 7540, higher: 1892, additional: 0 },
+  { taxableAnnualIncome: 60_000, basic: 7540, higher: 3892, additional: 0 },
+  { taxableAnnualIncome: 75_000, basic: 7540, higher: 9892, additional: 0 },
+  { taxableAnnualIncome: 90_000, basic: 7540, higher: 15892, additional: 0 },
+  { taxableAnnualIncome: 105_000, basic: 7540, higher: 22892, additional: 0 },
+  { taxableAnnualIncome: 110_000, basic: 7540, higher: 25892, additional: 0 },
+  {
+    taxableAnnualIncome: 130_000,
+    basic: 7540,
+    higher: 34976,
+    additional: 2187,
+  },
+  {
+    taxableAnnualIncome: 145_000,
+    basic: 7540,
+    higher: 34976,
+    additional: 8937,
+  },
+  {
+    taxableAnnualIncome: 160_000,
+    basic: 7540,
+    higher: 34976,
+    additional: 15687,
+  },
+  {
+    taxableAnnualIncome: 175_000,
+    basic: 7540,
+    higher: 34976,
+    additional: 22437,
+  },
+  {
+    taxableAnnualIncome: 200_000,
+    basic: 7540,
+    higher: 34976,
+    additional: 33687,
+  },
+  {
+    taxableAnnualIncome: 250_000,
+    basic: 7540,
+    higher: 34976,
+    additional: 56187,
+  },
+  {
+    taxableAnnualIncome: 500_000,
+    basic: 7540,
+    higher: 34976,
+    additional: 168687,
+  },
+  {
+    taxableAnnualIncome: 1_000_000,
+    basic: 7540,
+    higher: 34976,
+    additional: 393687,
+  },
+];
+
+describe("calculateIncomeTax (24/25)", () => {
+  expectationsB.forEach((expectation) => {
+    const { taxableAnnualIncome, basic, higher, additional } = expectation;
+    test(taxableAnnualIncome.toString(), () => {
+      const personalAllowance = calculatePersonalAllowance({
+        taxYear: "2024/25",
+        taxableAnnualIncome,
+      });
+      const taxAmounts = calculateIncomeTax({
+        taxYear: "2024/25",
+        taxableAnnualIncome,
+        personalAllowance,
+      });
+      expect(taxAmounts).toEqual({
+        basicRateTax: basic,
+        higherRateTax: higher,
+        additionalRateTax: additional,
+      });
+    });
+  });
+});

src/nationalInsurance.test.ts

@@ -69,3 +69,38 @@ describe("calculateEmployeeNationalInsurance (23/24)", () => {
     });
   });
 });
+
+const expectationsC = [
+  { taxableAnnualIncome: 15_000, nics: 193.28 },
+  { taxableAnnualIncome: 17_500, nics: 393.28 },
+  { taxableAnnualIncome: 20_000, nics: 593.28 },
+  { taxableAnnualIncome: 22_500, nics: 793.28 },
+  { taxableAnnualIncome: 25_000, nics: 993.28 },
+  { taxableAnnualIncome: 50_000, nics: 2993.28 },
+  { taxableAnnualIncome: 55_000, nics: 3110.32 },
+  { taxableAnnualIncome: 60_000, nics: 3210.32 },
+  { taxableAnnualIncome: 75_000, nics: 3510.32 },
+  { taxableAnnualIncome: 90_000, nics: 3810.32 },
+  { taxableAnnualIncome: 110_000, nics: 4210.32 },
+  { taxableAnnualIncome: 130_000, nics: 4610.32 },
+  { taxableAnnualIncome: 150_000, nics: 5010.32 },
+  { taxableAnnualIncome: 175_000, nics: 5510.32 },
+  { taxableAnnualIncome: 200_000, nics: 6010.32 },
+  { taxableAnnualIncome: 250_000, nics: 7010.32 },
+  { taxableAnnualIncome: 500_000, nics: 12010.32 },
+  { taxableAnnualIncome: 1_000_000, nics: 22010.32 },
+];
+
+describe("calculateEmployeeNationalInsurance (24/25)", () => {
+  expectationsC.forEach((expectation) => {
+    const { taxableAnnualIncome, nics } = expectation;
+    test(taxableAnnualIncome.toString(), () => {
+      expect(
+        calculateEmployeeNationalInsurance({
+          taxYear: "2024/25",
+          taxableAnnualIncome,
+        })
+      ).toBeCloseTo(nics, 1);
+    });
+  });
+});