From 51003f371e5b0197e9a03ea2c15b0b47f4267e69 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Fri, 1 May 2026 15:43:34 +0000
Subject: [PATCH 1/2] Add CPP/QPP enhanced contribution deduction (CRA line
 22215)

Models the deduction for the enhanced portion of CPP/QPP first-tier
contributions plus the entire CPP2/QPP2 contribution, applied against
taxable income for federal and provincial brackets per CRA line 22215.
Configs gain a `baseRate` (4.95% CPP, 5.40% QPP); the calculator computes
the enhanced share proportionally to the contribution and reduces the
income used for bracket calculations. The tax-visualizer surfaces the
deduction inline with the federal or provincial card depending on which
plan applies.

https://claude.ai/code/session_01DTfhD3S8sQTsuY5ggEQs26
---
 src/app/[lang]/(main)/tax-visualizer/page.tsx | 220 ++++++++++++++++--
 src/lib/tax/calculator.deduction.test.ts      |  78 +++++++
 src/lib/tax/calculator.ts                     |  59 +++--
 src/lib/tax/configs/2023/federal.ts           |   1 +
 src/lib/tax/configs/2023/quebec.ts            |   1 +
 src/lib/tax/configs/2024/federal.ts           |   1 +
 src/lib/tax/configs/2024/quebec.ts            |   1 +
 src/lib/tax/configs/2025/federal.ts           |   1 +
 src/lib/tax/configs/2025/quebec.ts            |   1 +
 src/lib/tax/configs/2026/federal.ts           |   1 +
 src/lib/tax/configs/2026/quebec.ts            |   1 +
 src/lib/tax/types.ts                          |   9 +-
 12 files changed, 333 insertions(+), 41 deletions(-)
 create mode 100644 src/lib/tax/calculator.deduction.test.ts

diff --git a/src/app/[lang]/(main)/tax-visualizer/page.tsx b/src/app/[lang]/(main)/tax-visualizer/page.tsx
index a60d5b5a..ed4f56b8 100644
--- a/src/app/[lang]/(main)/tax-visualizer/page.tsx
+++ b/src/app/[lang]/(main)/tax-visualizer/page.tsx
@@ -193,6 +193,8 @@ function IncomeTaxBracketsSection({
   title,
   config,
   income,
+  deduction = 0,
+  deductionLabel,
 }: {
   title: string;
   config: {
@@ -200,8 +202,11 @@ function IncomeTaxBracketsSection({
     basicPersonalAmount: number;
   };
   income: number;
+  deduction?: number;
+  deductionLabel?: string;
 }) {
-  const breakdown = getBracketTaxBreakdown(income, config.brackets);
+  const taxableIncome = Math.max(0, income - deduction);
+  const breakdown = getBracketTaxBreakdown(taxableIncome, config.brackets);
   const lowestRate = config.brackets[0]?.rate ?? 0;
   const bpaCredit = config.basicPersonalAmount * lowestRate;
   const totalBeforeCredit = breakdown.reduce((sum, b) => sum + b.taxAmount, 0);
@@ -210,6 +215,15 @@ function IncomeTaxBracketsSection({
   return (
     <div>
       <h4 className="font-semibold text-base mb-3">{title}</h4>
+      {deduction > 0 && (
+        <p className="text-xs text-muted-foreground mb-2">
+          <Trans>
+            Brackets applied to taxable income {formatAmount(taxableIncome)} (
+            {formatAmount(income)} less {formatAmount(deduction)}
+            {deductionLabel ? ` ${deductionLabel}` : ""})
+          </Trans>
+        </p>
+      )}
       <table className="w-full text-left">
         <thead>
           <tr>
@@ -282,16 +296,6 @@ function FederalTaxCard({
   provincialConfig,
   income,
 }: FederalTaxCardProps) {
-  // Calculate income tax
-  const breakdown = getBracketTaxBreakdown(income, config.incomeTax.brackets);
-  const lowestRate = config.incomeTax.brackets[0]?.rate ?? 0;
-  const bpaCredit = config.incomeTax.basicPersonalAmount * lowestRate;
-  const incomeTaxBeforeCredit = breakdown.reduce(
-    (sum, b) => sum + b.taxAmount,
-    0,
-  );
-  const incomeTaxAmount = Math.max(0, incomeTaxBeforeCredit - bpaCredit);
-
   // Resolve EI override (Quebec residents pay a reduced rate). The pension
   // plan, when overridden, is administered provincially (Retraite Québec)
   // and is rendered in the Provincial card instead.
@@ -306,6 +310,36 @@ function FederalTaxCard({
   const eiAmount = calculateCappedContribution(income, eiConfig);
   const payrollTotal = cppAmount + cpp2Amount + eiAmount;
 
+  // Line 22215 deduction is applied at the provincial level when the
+  // province administers its own pension plan (e.g., Quebec QPP), and at
+  // the federal level otherwise. This card reduces taxable income for the
+  // federal income tax bracket calculation only when CPP applies.
+  const cppEnhancedRate =
+    config.cpp.baseRate !== undefined
+      ? Math.max(0, config.cpp.rate - config.cpp.baseRate)
+      : 0;
+  const cppEnhancedPortion =
+    !hasProvincialPension && config.cpp.rate > 0
+      ? cppAmount * (cppEnhancedRate / config.cpp.rate)
+      : 0;
+  const cppQppEnhancedDeduction = hasProvincialPension
+    ? 0
+    : cppEnhancedPortion + cpp2Amount;
+
+  // Calculate income tax on taxable income (after the line 22215 deduction).
+  const taxableIncome = Math.max(0, income - cppQppEnhancedDeduction);
+  const breakdown = getBracketTaxBreakdown(
+    taxableIncome,
+    config.incomeTax.brackets,
+  );
+  const lowestRate = config.incomeTax.brackets[0]?.rate ?? 0;
+  const bpaCredit = config.incomeTax.basicPersonalAmount * lowestRate;
+  const incomeTaxBeforeCredit = breakdown.reduce(
+    (sum, b) => sum + b.taxAmount,
+    0,
+  );
+  const incomeTaxAmount = Math.max(0, incomeTaxBeforeCredit - bpaCredit);
+
   // Calculate federal abatement (Quebec Abatement)
   const federalAbatementConfig = provincialConfig.federalAbatement;
   const federalAbatementAmount = federalAbatementConfig
@@ -328,8 +362,62 @@ function FederalTaxCard({
           title={config.incomeTax.name}
           config={config.incomeTax}
           income={income}
+          deduction={cppQppEnhancedDeduction}
+          deductionLabel="CPP/CPP2 enhanced deduction (line 22215)"
         />
 
+        {/* CPP/CPP2 Enhanced Deduction (Line 22215) */}
+        {cppQppEnhancedDeduction > 0 && (
+          <div className="mt-6 pt-4 border-t border-border">
+            <h4 className="font-semibold text-base mb-2">
+              <Trans>
+                Deduction for CPP enhanced contributions (Line 22215)
+              </Trans>
+            </h4>
+            <table className="w-full text-left text-sm">
+              <tbody>
+                {cppEnhancedPortion > 0 && (
+                  <tr>
+                    <td className="py-1 text-muted-foreground">
+                      <div>
+                        <Trans>{config.cpp.shortName} enhanced portion</Trans>
+                      </div>
+                      <div className="text-xs text-muted-foreground/70">
+                        {formatPercent(cppEnhancedRate)} of pensionable earnings
+                      </div>
+                    </td>
+                    <td className="py-1 text-right font-medium align-top w-20 text-red-600">
+                      -{formatAmount(cppEnhancedPortion)}
+                    </td>
+                  </tr>
+                )}
+                {cpp2Amount > 0 && (
+                  <tr>
+                    <td className="py-1 text-muted-foreground">
+                      <div>
+                        <Trans>
+                          {config.cpp2.shortName} (fully deductible)
+                        </Trans>
+                      </div>
+                    </td>
+                    <td className="py-1 text-right font-medium align-top w-20 text-red-600">
+                      -{formatAmount(cpp2Amount)}
+                    </td>
+                  </tr>
+                )}
+                <tr className="font-semibold border-t border-border">
+                  <td className="py-1">
+                    <Trans>Total deduction from taxable income</Trans>
+                  </td>
+                  <td className="py-1 text-right w-20 text-red-600">
+                    -{formatAmount(cppQppEnhancedDeduction)}
+                  </td>
+                </tr>
+              </tbody>
+            </table>
+          </div>
+        )}
+
         {/* Federal Abatement (if applicable) */}
         {federalAbatementConfig && federalAbatementAmount > 0 && (
           <div className="mt-6 pt-4 border-t border-border">
@@ -443,19 +531,6 @@ function ProvincialTaxCard({
   config,
   income,
 }: ProvincialTaxCardProps) {
-  // Calculate provincial income tax for surtax calculation
-  const breakdown = getBracketTaxBreakdown(income, config.incomeTax.brackets);
-  const lowestRate = config.incomeTax.brackets[0]?.rate ?? 0;
-  const bpaCredit = config.incomeTax.basicPersonalAmount * lowestRate;
-  const provincialTaxBeforeCredit = breakdown.reduce(
-    (sum, b) => sum + b.taxAmount,
-    0,
-  );
-  const provincialTax = Math.max(0, provincialTaxBeforeCredit - bpaCredit);
-
-  const surtaxAmount = config.surtax
-    ? calculateSurtax(provincialTax, config.surtax)
-    : 0;
   const healthPremiumAmount = config.healthPremium
     ? calculateHealthPremium(income, config.healthPremium)
     : 0;
@@ -470,6 +545,44 @@ function ProvincialTaxCard({
     ? calculateCpp2Contribution(income, config.pensionPlanAdditionalOverride)
     : 0;
 
+  // QPP enhanced deduction (line 22215) — applies when the province has its
+  // own pension plan (e.g., Quebec QPP). For provinces that use the federal
+  // CPP, the deduction is shown on the federal card.
+  const qppEnhancedRate =
+    config.pensionPlanOverride?.baseRate !== undefined
+      ? Math.max(
+          0,
+          config.pensionPlanOverride.rate - config.pensionPlanOverride.baseRate,
+        )
+      : 0;
+  const qppEnhancedPortion =
+    config.pensionPlanOverride && config.pensionPlanOverride.rate > 0
+      ? provincialPensionAmount *
+        (qppEnhancedRate / config.pensionPlanOverride.rate)
+      : 0;
+  const qppEnhancedDeduction = config.pensionPlanOverride
+    ? qppEnhancedPortion + provincialPensionAdditionalAmount
+    : 0;
+
+  // Calculate provincial income tax on taxable income (after line 22215
+  // deduction when applicable).
+  const taxableIncome = Math.max(0, income - qppEnhancedDeduction);
+  const breakdown = getBracketTaxBreakdown(
+    taxableIncome,
+    config.incomeTax.brackets,
+  );
+  const lowestRate = config.incomeTax.brackets[0]?.rate ?? 0;
+  const bpaCredit = config.incomeTax.basicPersonalAmount * lowestRate;
+  const provincialTaxBeforeCredit = breakdown.reduce(
+    (sum, b) => sum + b.taxAmount,
+    0,
+  );
+  const provincialTax = Math.max(0, provincialTaxBeforeCredit - bpaCredit);
+
+  const surtaxAmount = config.surtax
+    ? calculateSurtax(provincialTax, config.surtax)
+    : 0;
+
   // Overall total
   const totalProvincialTax =
     provincialTax +
@@ -491,8 +604,67 @@ function ProvincialTaxCard({
           title={config.incomeTax.name}
           config={config.incomeTax}
           income={income}
+          deduction={qppEnhancedDeduction}
+          deductionLabel="QPP/QPP2 enhanced deduction (line 22215)"
         />
 
+        {/* QPP/QPP2 Enhanced Deduction (Line 22215) */}
+        {qppEnhancedDeduction > 0 && config.pensionPlanOverride && (
+          <div className="mt-6 pt-4 border-t border-border">
+            <h4 className="font-semibold text-base mb-2">
+              <Trans>
+                Deduction for QPP enhanced contributions (Line 22215)
+              </Trans>
+            </h4>
+            <table className="w-full text-left text-sm">
+              <tbody>
+                {qppEnhancedPortion > 0 && (
+                  <tr>
+                    <td className="py-1 text-muted-foreground">
+                      <div>
+                        <Trans>
+                          {config.pensionPlanOverride.shortName} enhanced
+                          portion
+                        </Trans>
+                      </div>
+                      <div className="text-xs text-muted-foreground/70">
+                        {formatPercent(qppEnhancedRate)} of pensionable earnings
+                      </div>
+                    </td>
+                    <td className="py-1 text-right font-medium align-top w-20 text-red-600">
+                      -{formatAmount(qppEnhancedPortion)}
+                    </td>
+                  </tr>
+                )}
+                {provincialPensionAdditionalAmount > 0 &&
+                  config.pensionPlanAdditionalOverride && (
+                    <tr>
+                      <td className="py-1 text-muted-foreground">
+                        <div>
+                          <Trans>
+                            {config.pensionPlanAdditionalOverride.shortName}{" "}
+                            (fully deductible)
+                          </Trans>
+                        </div>
+                      </td>
+                      <td className="py-1 text-right font-medium align-top w-20 text-red-600">
+                        -{formatAmount(provincialPensionAdditionalAmount)}
+                      </td>
+                    </tr>
+                  )}
+                <tr className="font-semibold border-t border-border">
+                  <td className="py-1">
+                    <Trans>Total deduction from taxable income</Trans>
+                  </td>
+                  <td className="py-1 text-right w-20 text-red-600">
+                    -{formatAmount(qppEnhancedDeduction)}
+                  </td>
+                </tr>
+              </tbody>
+            </table>
+          </div>
+        )}
+
         {/* Surtax (if applicable) */}
         {config.surtax && (
           <div className="mt-6 pt-4 border-t border-border">
diff --git a/src/lib/tax/calculator.deduction.test.ts b/src/lib/tax/calculator.deduction.test.ts
new file mode 100644
index 00000000..e907e07c
--- /dev/null
+++ b/src/lib/tax/calculator.deduction.test.ts
@@ -0,0 +1,78 @@
+import { describe, expect, it } from "vitest";
+
+import { calculateDetailedTax } from "./calculator";
+
+// CRA line 22215: deduction for the "enhanced" portion of CPP/QPP
+// contributions on employment income.
+// - For CPP: the rate above the pre-2019 base of 4.95% (currently 1.0%)
+//   on first-tier pensionable earnings is deductible, plus 100% of CPP2.
+// - For QPP: the rate above the pre-2019 base of 5.40% on first-tier
+//   pensionable earnings is deductible, plus 100% of QPP2.
+
+describe("CPP/QPP enhanced contribution deduction (line 22215)", () => {
+  it("computes CPP enhanced deduction for Ontario 2024 above YMPE", () => {
+    // 2024 CPP: rate 5.95%, base 4.95%, exemption $3,500, YMPE $68,500.
+    // CPP1 = ($68,500 − $3,500) × 5.95% = $3,867.50
+    // Enhanced portion = $3,867.50 × (1.0% / 5.95%) = $650.00
+    // CPP2 = ($73,200 − $68,500) × 4% = $188.00 (fully deductible)
+    // Total deduction = $650.00 + $188.00 = $838.00
+    const detailed = calculateDetailedTax(80000, "ontario", "2024");
+    expect(detailed.cppQppEnhancedDeduction).toBeCloseTo(838, 2);
+  });
+
+  it("computes QPP enhanced deduction for Quebec 2024 above YMPE", () => {
+    // 2024 QPP: rate 6.40%, base 5.40%, exemption $3,500, YMPE $68,500.
+    // QPP1 = ($68,500 − $3,500) × 6.40% = $4,160.00
+    // Enhanced portion = $4,160.00 × (1.0% / 6.40%) = $650.00
+    // QPP2 = ($73,200 − $68,500) × 4% = $188.00 (fully deductible)
+    // Total deduction = $650.00 + $188.00 = $838.00
+    const detailed = calculateDetailedTax(80000, "quebec", "2024");
+    expect(detailed.cppQppEnhancedDeduction).toBeCloseTo(838, 2);
+  });
+
+  it("scales the deduction proportionally for low income", () => {
+    // 2024 Ontario at $30,000:
+    // CPP1 = ($30,000 − $3,500) × 5.95% = $1,576.75
+    // Enhanced portion = $1,576.75 × (1.0% / 5.95%) ≈ $264.99
+    // CPP2 = 0 (income below YMPE)
+    const detailed = calculateDetailedTax(30000, "ontario", "2024");
+    expect(detailed.cppQppEnhancedDeduction).toBeCloseTo(264.99, 1);
+  });
+
+  it("reduces federal income tax by deducting enhanced contributions", () => {
+    // Without the deduction, federal income tax at $80k Ontario 2024 would be
+    // higher. With the $838 deduction, tax is lowered by ~ $838 × 20.5%
+    // (the marginal bracket the deduction comes off of).
+    const detailedWithLine22215 = calculateDetailedTax(
+      80000,
+      "ontario",
+      "2024",
+    );
+
+    // Verify the deduction at least reduces taxable income (federal tax is
+    // computed on income − deduction). The exact federal tax is checked via
+    // the bracket calculator in other tests; here we just confirm the
+    // deduction takes effect.
+    expect(detailedWithLine22215.cppQppEnhancedDeduction).toBeGreaterThan(0);
+    expect(detailedWithLine22215.federalIncomeTax).toBeGreaterThan(0);
+  });
+
+  it("reports the deduction as a negative line item at the federal level for non-Quebec", () => {
+    const detailed = calculateDetailedTax(80000, "ontario", "2024");
+    const line = detailed.lineItems.find(
+      (l) => l.id === "cpp-qpp-enhanced-deduction",
+    );
+    expect(line).toBeDefined();
+    expect(line!.amount).toBeLessThan(0);
+    expect(line!.level).toBe("federal");
+  });
+
+  it("reports the deduction at the provincial level for Quebec", () => {
+    const detailed = calculateDetailedTax(80000, "quebec", "2024");
+    const line = detailed.lineItems.find(
+      (l) => l.id === "cpp-qpp-enhanced-deduction",
+    );
+    expect(line).toBeDefined();
+    expect(line!.level).toBe("provincial");
+  });
+});
diff --git a/src/lib/tax/calculator.ts b/src/lib/tax/calculator.ts
index b626aa73..edbd4dd4 100644
--- a/src/lib/tax/calculator.ts
+++ b/src/lib/tax/calculator.ts
@@ -58,20 +58,6 @@ function calculateWithConfig(
     ? "provincial"
     : "federal";
 
-  // Federal income tax
-  const federalIncomeTax = calculateBracketTax(
-    income,
-    config.federal.incomeTax,
-  );
-  lineItems.push({
-    id: "federal-income-tax",
-    name: "Federal Income Tax",
-    level: "federal",
-    amount: federalIncomeTax,
-    effectiveRate: income > 0 ? (federalIncomeTax / income) * 100 : 0,
-    category: "incomeTax",
-  });
-
   // EI contribution (Quebec residents pay a reduced rate; see eiConfig)
   const eiContribution = calculateCappedContribution(income, eiConfig);
   lineItems.push({
@@ -130,9 +116,49 @@ function calculateWithConfig(
     }
   }
 
-  // Provincial income tax
+  // CRA line 22215: deduction for the "enhanced" portion of CPP/QPP
+  // contributions on employment income. The first-additional enhancement
+  // (rate above pre-2019 baseRate) and the entire second-additional
+  // contribution (CPP2/QPP2) are deductible from taxable income.
+  const cppEnhancedRate =
+    pensionConfig.baseRate !== undefined
+      ? Math.max(0, pensionConfig.rate - pensionConfig.baseRate)
+      : 0;
+  const cppEnhancedPortion =
+    pensionConfig.rate > 0
+      ? cppContribution * (cppEnhancedRate / pensionConfig.rate)
+      : 0;
+  const cppQppEnhancedDeduction = cppEnhancedPortion + cpp2Contribution;
+  const taxableIncome = Math.max(0, income - cppQppEnhancedDeduction);
+  if (cppQppEnhancedDeduction > 0) {
+    lineItems.push({
+      id: "cpp-qpp-enhanced-deduction",
+      name: "Deduction for CPP/QPP Enhanced Contributions",
+      level: pensionLevel,
+      amount: -cppQppEnhancedDeduction,
+      effectiveRate: income > 0 ? (-cppQppEnhancedDeduction / income) * 100 : 0,
+      category: "cppQppEnhancedDeduction",
+    });
+  }
+
+  // Federal income tax (computed on taxable income after the line 22215
+  // deduction).
+  const federalIncomeTax = calculateBracketTax(
+    taxableIncome,
+    config.federal.incomeTax,
+  );
+  lineItems.push({
+    id: "federal-income-tax",
+    name: "Federal Income Tax",
+    level: "federal",
+    amount: federalIncomeTax,
+    effectiveRate: income > 0 ? (federalIncomeTax / income) * 100 : 0,
+    category: "incomeTax",
+  });
+
+  // Provincial income tax (also on taxable income after the deduction).
   const provincialIncomeTax = calculateBracketTax(
-    income,
+    taxableIncome,
     config.provincial.incomeTax,
   );
   const provinceName =
@@ -241,6 +267,7 @@ function calculateWithConfig(
     surtax,
     healthPremium,
     federalAbatement,
+    cppQppEnhancedDeduction,
 
     // Metadata
     year: config.year,
diff --git a/src/lib/tax/configs/2023/federal.ts b/src/lib/tax/configs/2023/federal.ts
index 5e2354c1..0d70ebbd 100644
--- a/src/lib/tax/configs/2023/federal.ts
+++ b/src/lib/tax/configs/2023/federal.ts
@@ -27,6 +27,7 @@ export const FEDERAL_TAX_CONFIG: FederalTaxConfig = {
     name: "Canada Pension Plan",
     shortName: "CPP",
     rate: 0.0595,
+    baseRate: 0.0495,
     exemption: 3500,
     maxEarnings: 66600,
     maxContribution: 3754.45,
diff --git a/src/lib/tax/configs/2023/quebec.ts b/src/lib/tax/configs/2023/quebec.ts
index 6ad1f1aa..c5c9e52c 100644
--- a/src/lib/tax/configs/2023/quebec.ts
+++ b/src/lib/tax/configs/2023/quebec.ts
@@ -37,6 +37,7 @@ export const QUEBEC_TAX_CONFIG: ProvincialTaxConfig = {
     name: "Québec Pension Plan",
     shortName: "QPP",
     rate: 0.064,
+    baseRate: 0.054,
     exemption: 3500,
     maxEarnings: 66600,
     maxContribution: 4038.4,
diff --git a/src/lib/tax/configs/2024/federal.ts b/src/lib/tax/configs/2024/federal.ts
index 8a449043..6c934808 100644
--- a/src/lib/tax/configs/2024/federal.ts
+++ b/src/lib/tax/configs/2024/federal.ts
@@ -27,6 +27,7 @@ export const FEDERAL_TAX_CONFIG: FederalTaxConfig = {
     name: "Canada Pension Plan",
     shortName: "CPP",
     rate: 0.0595,
+    baseRate: 0.0495,
     exemption: 3500,
     maxEarnings: 68500,
     maxContribution: 3867.5,
diff --git a/src/lib/tax/configs/2024/quebec.ts b/src/lib/tax/configs/2024/quebec.ts
index 1d82e783..07066aec 100644
--- a/src/lib/tax/configs/2024/quebec.ts
+++ b/src/lib/tax/configs/2024/quebec.ts
@@ -39,6 +39,7 @@ export const QUEBEC_TAX_CONFIG: ProvincialTaxConfig = {
     name: "Québec Pension Plan",
     shortName: "QPP",
     rate: 0.064,
+    baseRate: 0.054,
     exemption: 3500,
     maxEarnings: 68500,
     maxContribution: 4160,
diff --git a/src/lib/tax/configs/2025/federal.ts b/src/lib/tax/configs/2025/federal.ts
index f7832d88..fc861737 100644
--- a/src/lib/tax/configs/2025/federal.ts
+++ b/src/lib/tax/configs/2025/federal.ts
@@ -27,6 +27,7 @@ export const FEDERAL_TAX_CONFIG: FederalTaxConfig = {
     name: "Canada Pension Plan",
     shortName: "CPP",
     rate: 0.0595,
+    baseRate: 0.0495,
     exemption: 3500,
     maxEarnings: 71300,
     maxContribution: 4034.1,
diff --git a/src/lib/tax/configs/2025/quebec.ts b/src/lib/tax/configs/2025/quebec.ts
index 21e79101..2a8ee09f 100644
--- a/src/lib/tax/configs/2025/quebec.ts
+++ b/src/lib/tax/configs/2025/quebec.ts
@@ -38,6 +38,7 @@ export const QUEBEC_TAX_CONFIG: ProvincialTaxConfig = {
     name: "Québec Pension Plan",
     shortName: "QPP",
     rate: 0.064,
+    baseRate: 0.054,
     exemption: 3500,
     maxEarnings: 71300,
     maxContribution: 4339.2,
diff --git a/src/lib/tax/configs/2026/federal.ts b/src/lib/tax/configs/2026/federal.ts
index a2b33568..44b636f2 100644
--- a/src/lib/tax/configs/2026/federal.ts
+++ b/src/lib/tax/configs/2026/federal.ts
@@ -27,6 +27,7 @@ export const FEDERAL_TAX_CONFIG: FederalTaxConfig = {
     name: "Canada Pension Plan",
     shortName: "CPP",
     rate: 0.0595,
+    baseRate: 0.0495,
     exemption: 3500,
     maxEarnings: 74600,
     maxContribution: 4230.45,
diff --git a/src/lib/tax/configs/2026/quebec.ts b/src/lib/tax/configs/2026/quebec.ts
index 97348d75..dfe32b79 100644
--- a/src/lib/tax/configs/2026/quebec.ts
+++ b/src/lib/tax/configs/2026/quebec.ts
@@ -45,6 +45,7 @@ export const QUEBEC_TAX_CONFIG: ProvincialTaxConfig = {
     name: "Québec Pension Plan",
     shortName: "QPP",
     rate: 0.063,
+    baseRate: 0.054,
     exemption: 3500,
     maxEarnings: 74600,
     maxContribution: 4479.3,
diff --git a/src/lib/tax/types.ts b/src/lib/tax/types.ts
index 2f81684d..c281ee23 100644
--- a/src/lib/tax/types.ts
+++ b/src/lib/tax/types.ts
@@ -22,6 +22,11 @@ export interface CappedContributionConfig {
   exemption: number;
   maxEarnings: number;
   maxContribution: number;
+  // For CPP/QPP: the historical "base" rate (pre-2019 enhancement). The
+  // portion of the contribution attributable to (rate - baseRate) is the
+  // "enhanced" CPP/QPP contribution and is deductible from taxable income
+  // on CRA line 22215. If unset, no enhanced deduction is computed.
+  baseRate?: number;
 }
 
 // Surtax config (Ontario surtax - tiers applied to base tax)
@@ -135,7 +140,8 @@ export interface TaxLineItem {
     | "healthPremium"
     | "incomeTaxProvincial"
     | "federalAbatement"
-    | "parentalInsurance";
+    | "parentalInsurance"
+    | "cppQppEnhancedDeduction";
 }
 
 // Detailed calculation result
@@ -161,6 +167,7 @@ export interface DetailedTaxCalculation {
   surtax: number;
   healthPremium: number;
   federalAbatement: number;
+  cppQppEnhancedDeduction: number;
 
   // Metadata
   year: string;

From 9434e4e50b4b4fa7bdb3cba46294df7ef9b284ba Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Fri, 1 May 2026 20:31:14 +0000
Subject: [PATCH 2/2] Move line 22215 deduction into Total Taxable Income
 summary
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Restructure each tax card so the line 22215 CPP/QPP enhanced deduction
is visualized as a reduction to taxable income — not as a credit against
total tax owing. Each card now leads with a "Total Taxable Income" line,
with the gross income and per-contribution deduction details collapsed
behind an expandable <details> summary. The deduction is computed once
in TaxDetails and shared with both the Federal and Provincial cards so
their bracket calculations apply to the same taxable income.

https://claude.ai/code/session_01DTfhD3S8sQTsuY5ggEQs26
---
 src/app/[lang]/(main)/tax-visualizer/page.tsx | 347 +++++++++---------
 1 file changed, 168 insertions(+), 179 deletions(-)

diff --git a/src/app/[lang]/(main)/tax-visualizer/page.tsx b/src/app/[lang]/(main)/tax-visualizer/page.tsx
index ed4f56b8..e2c092ae 100644
--- a/src/app/[lang]/(main)/tax-visualizer/page.tsx
+++ b/src/app/[lang]/(main)/tax-visualizer/page.tsx
@@ -193,8 +193,6 @@ function IncomeTaxBracketsSection({
   title,
   config,
   income,
-  deduction = 0,
-  deductionLabel,
 }: {
   title: string;
   config: {
@@ -202,11 +200,8 @@ function IncomeTaxBracketsSection({
     basicPersonalAmount: number;
   };
   income: number;
-  deduction?: number;
-  deductionLabel?: string;
 }) {
-  const taxableIncome = Math.max(0, income - deduction);
-  const breakdown = getBracketTaxBreakdown(taxableIncome, config.brackets);
+  const breakdown = getBracketTaxBreakdown(income, config.brackets);
   const lowestRate = config.brackets[0]?.rate ?? 0;
   const bpaCredit = config.basicPersonalAmount * lowestRate;
   const totalBeforeCredit = breakdown.reduce((sum, b) => sum + b.taxAmount, 0);
@@ -215,15 +210,6 @@ function IncomeTaxBracketsSection({
   return (
     <div>
       <h4 className="font-semibold text-base mb-3">{title}</h4>
-      {deduction > 0 && (
-        <p className="text-xs text-muted-foreground mb-2">
-          <Trans>
-            Brackets applied to taxable income {formatAmount(taxableIncome)} (
-            {formatAmount(income)} less {formatAmount(deduction)}
-            {deductionLabel ? ` ${deductionLabel}` : ""})
-          </Trans>
-        </p>
-      )}
       <table className="w-full text-left">
         <thead>
           <tr>
@@ -284,21 +270,154 @@ function IncomeTaxBracketsSection({
   );
 }
 
+interface DeductionItem {
+  label: string;
+  sublabel?: string;
+  amount: number;
+}
+
+interface TaxableIncomeBreakdown {
+  taxableIncome: number;
+  deductionTotal: number;
+  deductionItems: DeductionItem[];
+}
+
+// Compute the line 22215 CPP/QPP enhanced-contribution deduction for the
+// active province. The deduction reduces taxable income for both federal
+// and provincial brackets, so it's computed once and shared by both cards.
+function computeTaxableIncomeBreakdown(
+  income: number,
+  config: TaxYearProvinceConfig,
+): TaxableIncomeBreakdown {
+  const pensionConfig =
+    config.provincial.pensionPlanOverride ?? config.federal.cpp;
+  const pensionAdditionalConfig =
+    config.provincial.pensionPlanAdditionalOverride ?? config.federal.cpp2;
+  const pensionAmount = calculateCappedContribution(income, pensionConfig);
+  const pensionAdditionalAmount = calculateCpp2Contribution(
+    income,
+    pensionAdditionalConfig,
+  );
+  const enhancedRate =
+    pensionConfig.baseRate !== undefined
+      ? Math.max(0, pensionConfig.rate - pensionConfig.baseRate)
+      : 0;
+  const enhancedPortion =
+    pensionConfig.rate > 0
+      ? pensionAmount * (enhancedRate / pensionConfig.rate)
+      : 0;
+  const deductionTotal = enhancedPortion + pensionAdditionalAmount;
+  const taxableIncome = Math.max(0, income - deductionTotal);
+
+  const deductionItems: DeductionItem[] = [];
+  if (enhancedPortion > 0) {
+    deductionItems.push({
+      label: `${pensionConfig.shortName} enhanced portion (line 22215)`,
+      sublabel: `${formatPercent(enhancedRate)} of pensionable earnings`,
+      amount: enhancedPortion,
+    });
+  }
+  if (pensionAdditionalAmount > 0) {
+    deductionItems.push({
+      label: `${pensionAdditionalConfig.shortName} (line 22215, fully deductible)`,
+      amount: pensionAdditionalAmount,
+    });
+  }
+
+  return { taxableIncome, deductionTotal, deductionItems };
+}
+
+// Taxable income section: shows gross income reduced by the line 22215
+// CPP/QPP enhanced contribution deduction. The deduction detail is hidden
+// behind an expandable `<details>` so it doesn't read as a reduction in
+// total tax owing.
+function TaxableIncomeSection({
+  income,
+  taxableIncome,
+  deductionItems,
+  deductionTotal,
+}: {
+  income: number;
+  taxableIncome: number;
+  deductionItems: DeductionItem[];
+  deductionTotal: number;
+}) {
+  const hasDeduction = deductionTotal > 0;
+
+  return (
+    <div className="mb-6">
+      <div className="flex justify-between items-baseline">
+        <h4 className="font-semibold text-base">
+          <Trans>Total Taxable Income</Trans>
+        </h4>
+        <span className="font-semibold text-base">
+          {formatAmount(taxableIncome)}
+        </span>
+      </div>
+      {hasDeduction && (
+        <details className="mt-2 group">
+          <summary className="cursor-pointer text-xs text-muted-foreground hover:text-foreground select-none">
+            <Trans>
+              {formatAmount(income)} gross income less{" "}
+              {formatAmount(deductionTotal)} CPP/QPP enhanced deduction (line
+              22215)
+            </Trans>
+          </summary>
+          <table className="w-full text-left text-sm mt-2">
+            <tbody>
+              <tr>
+                <td className="py-1 text-muted-foreground">
+                  <Trans>Gross employment income</Trans>
+                </td>
+                <td className="py-1 text-right font-medium w-24">
+                  {formatAmount(income)}
+                </td>
+              </tr>
+              {deductionItems.map((item, index) => (
+                <tr key={index}>
+                  <td className="py-1 text-muted-foreground">
+                    <div>{item.label}</div>
+                    {item.sublabel && (
+                      <div className="text-xs text-muted-foreground/70">
+                        {item.sublabel}
+                      </div>
+                    )}
+                  </td>
+                  <td className="py-1 text-right font-medium align-top w-24 text-red-600">
+                    -{formatAmount(item.amount)}
+                  </td>
+                </tr>
+              ))}
+              <tr className="font-semibold border-t border-border">
+                <td className="py-1">
+                  <Trans>Taxable income</Trans>
+                </td>
+                <td className="py-1 text-right w-24">
+                  {formatAmount(taxableIncome)}
+                </td>
+              </tr>
+            </tbody>
+          </table>
+        </details>
+      )}
+    </div>
+  );
+}
+
 // Federal Tax Card - all federal taxes in one card
 interface FederalTaxCardProps {
   config: TaxYearProvinceConfig["federal"];
   provincialConfig: TaxYearProvinceConfig["provincial"];
   income: number;
+  taxableBreakdown: TaxableIncomeBreakdown;
 }
 
 function FederalTaxCard({
   config,
   provincialConfig,
   income,
+  taxableBreakdown,
 }: FederalTaxCardProps) {
-  // Resolve EI override (Quebec residents pay a reduced rate). The pension
-  // plan, when overridden, is administered provincially (Retraite Québec)
-  // and is rendered in the Provincial card instead.
   const eiConfig = provincialConfig.eiOverride ?? config.ei;
   const hasProvincialPension = !!provincialConfig.pensionPlanOverride;
   const cppAmount = hasProvincialPension
@@ -310,24 +429,9 @@ function FederalTaxCard({
   const eiAmount = calculateCappedContribution(income, eiConfig);
   const payrollTotal = cppAmount + cpp2Amount + eiAmount;
 
-  // Line 22215 deduction is applied at the provincial level when the
-  // province administers its own pension plan (e.g., Quebec QPP), and at
-  // the federal level otherwise. This card reduces taxable income for the
-  // federal income tax bracket calculation only when CPP applies.
-  const cppEnhancedRate =
-    config.cpp.baseRate !== undefined
-      ? Math.max(0, config.cpp.rate - config.cpp.baseRate)
-      : 0;
-  const cppEnhancedPortion =
-    !hasProvincialPension && config.cpp.rate > 0
-      ? cppAmount * (cppEnhancedRate / config.cpp.rate)
-      : 0;
-  const cppQppEnhancedDeduction = hasProvincialPension
-    ? 0
-    : cppEnhancedPortion + cpp2Amount;
-
-  // Calculate income tax on taxable income (after the line 22215 deduction).
-  const taxableIncome = Math.max(0, income - cppQppEnhancedDeduction);
+  // Federal income tax is computed on taxable income (after the line 22215
+  // CPP/QPP enhanced deduction).
+  const { taxableIncome } = taxableBreakdown;
   const breakdown = getBracketTaxBreakdown(
     taxableIncome,
     config.incomeTax.brackets,
@@ -340,13 +444,11 @@ function FederalTaxCard({
   );
   const incomeTaxAmount = Math.max(0, incomeTaxBeforeCredit - bpaCredit);
 
-  // Calculate federal abatement (Quebec Abatement)
   const federalAbatementConfig = provincialConfig.federalAbatement;
   const federalAbatementAmount = federalAbatementConfig
     ? incomeTaxAmount * federalAbatementConfig.rate
     : 0;
 
-  // Overall total (minus abatement)
   const totalFederalTax =
     incomeTaxAmount + payrollTotal - federalAbatementAmount;
 
@@ -357,67 +459,21 @@ function FederalTaxCard({
           <Trans>Federal Taxes</Trans>
         </h3>
 
-        {/* Income Tax Brackets */}
+        {/* Taxable Income (with line 22215 deduction details collapsed) */}
+        <TaxableIncomeSection
+          income={income}
+          taxableIncome={taxableBreakdown.taxableIncome}
+          deductionItems={taxableBreakdown.deductionItems}
+          deductionTotal={taxableBreakdown.deductionTotal}
+        />
+
+        {/* Income Tax Brackets (applied to taxable income) */}
         <IncomeTaxBracketsSection
           title={config.incomeTax.name}
           config={config.incomeTax}
-          income={income}
-          deduction={cppQppEnhancedDeduction}
-          deductionLabel="CPP/CPP2 enhanced deduction (line 22215)"
+          income={taxableIncome}
         />
 
-        {/* CPP/CPP2 Enhanced Deduction (Line 22215) */}
-        {cppQppEnhancedDeduction > 0 && (
-          <div className="mt-6 pt-4 border-t border-border">
-            <h4 className="font-semibold text-base mb-2">
-              <Trans>
-                Deduction for CPP enhanced contributions (Line 22215)
-              </Trans>
-            </h4>
-            <table className="w-full text-left text-sm">
-              <tbody>
-                {cppEnhancedPortion > 0 && (
-                  <tr>
-                    <td className="py-1 text-muted-foreground">
-                      <div>
-                        <Trans>{config.cpp.shortName} enhanced portion</Trans>
-                      </div>
-                      <div className="text-xs text-muted-foreground/70">
-                        {formatPercent(cppEnhancedRate)} of pensionable earnings
-                      </div>
-                    </td>
-                    <td className="py-1 text-right font-medium align-top w-20 text-red-600">
-                      -{formatAmount(cppEnhancedPortion)}
-                    </td>
-                  </tr>
-                )}
-                {cpp2Amount > 0 && (
-                  <tr>
-                    <td className="py-1 text-muted-foreground">
-                      <div>
-                        <Trans>
-                          {config.cpp2.shortName} (fully deductible)
-                        </Trans>
-                      </div>
-                    </td>
-                    <td className="py-1 text-right font-medium align-top w-20 text-red-600">
-                      -{formatAmount(cpp2Amount)}
-                    </td>
-                  </tr>
-                )}
-                <tr className="font-semibold border-t border-border">
-                  <td className="py-1">
-                    <Trans>Total deduction from taxable income</Trans>
-                  </td>
-                  <td className="py-1 text-right w-20 text-red-600">
-                    -{formatAmount(cppQppEnhancedDeduction)}
-                  </td>
-                </tr>
-              </tbody>
-            </table>
-          </div>
-        )}
-
         {/* Federal Abatement (if applicable) */}
         {federalAbatementConfig && federalAbatementAmount > 0 && (
           <div className="mt-6 pt-4 border-t border-border">
@@ -524,12 +580,14 @@ interface ProvincialTaxCardProps {
   provinceName: string;
   config: TaxYearProvinceConfig["provincial"];
   income: number;
+  taxableBreakdown: TaxableIncomeBreakdown;
 }
 
 function ProvincialTaxCard({
   provinceName,
   config,
   income,
+  taxableBreakdown,
 }: ProvincialTaxCardProps) {
   const healthPremiumAmount = config.healthPremium
     ? calculateHealthPremium(income, config.healthPremium)
@@ -537,7 +595,6 @@ function ProvincialTaxCard({
   const parentalInsuranceAmount = config.parentalInsurance
     ? calculateCappedContribution(income, config.parentalInsurance)
     : 0;
-  // Province-administered pension plan (e.g., Quebec QPP / QPP2)
   const provincialPensionAmount = config.pensionPlanOverride
     ? calculateCappedContribution(income, config.pensionPlanOverride)
     : 0;
@@ -545,28 +602,9 @@ function ProvincialTaxCard({
     ? calculateCpp2Contribution(income, config.pensionPlanAdditionalOverride)
     : 0;
 
-  // QPP enhanced deduction (line 22215) — applies when the province has its
-  // own pension plan (e.g., Quebec QPP). For provinces that use the federal
-  // CPP, the deduction is shown on the federal card.
-  const qppEnhancedRate =
-    config.pensionPlanOverride?.baseRate !== undefined
-      ? Math.max(
-          0,
-          config.pensionPlanOverride.rate - config.pensionPlanOverride.baseRate,
-        )
-      : 0;
-  const qppEnhancedPortion =
-    config.pensionPlanOverride && config.pensionPlanOverride.rate > 0
-      ? provincialPensionAmount *
-        (qppEnhancedRate / config.pensionPlanOverride.rate)
-      : 0;
-  const qppEnhancedDeduction = config.pensionPlanOverride
-    ? qppEnhancedPortion + provincialPensionAdditionalAmount
-    : 0;
-
-  // Calculate provincial income tax on taxable income (after line 22215
-  // deduction when applicable).
-  const taxableIncome = Math.max(0, income - qppEnhancedDeduction);
+  // Provincial income tax is computed on taxable income (after the line
+  // 22215 CPP/QPP enhanced deduction).
+  const { taxableIncome } = taxableBreakdown;
   const breakdown = getBracketTaxBreakdown(
     taxableIncome,
     config.incomeTax.brackets,
@@ -583,7 +621,6 @@ function ProvincialTaxCard({
     ? calculateSurtax(provincialTax, config.surtax)
     : 0;
 
-  // Overall total
   const totalProvincialTax =
     provincialTax +
     surtaxAmount +
@@ -599,72 +636,21 @@ function ProvincialTaxCard({
           <Trans>{provinceName} Taxes</Trans>
         </h3>
 
-        {/* Income Tax Brackets */}
+        {/* Taxable Income (with line 22215 deduction details collapsed) */}
+        <TaxableIncomeSection
+          income={income}
+          taxableIncome={taxableBreakdown.taxableIncome}
+          deductionItems={taxableBreakdown.deductionItems}
+          deductionTotal={taxableBreakdown.deductionTotal}
+        />
+
+        {/* Income Tax Brackets (applied to taxable income) */}
         <IncomeTaxBracketsSection
           title={config.incomeTax.name}
           config={config.incomeTax}
-          income={income}
-          deduction={qppEnhancedDeduction}
-          deductionLabel="QPP/QPP2 enhanced deduction (line 22215)"
+          income={taxableIncome}
         />
 
-        {/* QPP/QPP2 Enhanced Deduction (Line 22215) */}
-        {qppEnhancedDeduction > 0 && config.pensionPlanOverride && (
-          <div className="mt-6 pt-4 border-t border-border">
-            <h4 className="font-semibold text-base mb-2">
-              <Trans>
-                Deduction for QPP enhanced contributions (Line 22215)
-              </Trans>
-            </h4>
-            <table className="w-full text-left text-sm">
-              <tbody>
-                {qppEnhancedPortion > 0 && (
-                  <tr>
-                    <td className="py-1 text-muted-foreground">
-                      <div>
-                        <Trans>
-                          {config.pensionPlanOverride.shortName} enhanced
-                          portion
-                        </Trans>
-                      </div>
-                      <div className="text-xs text-muted-foreground/70">
-                        {formatPercent(qppEnhancedRate)} of pensionable earnings
-                      </div>
-                    </td>
-                    <td className="py-1 text-right font-medium align-top w-20 text-red-600">
-                      -{formatAmount(qppEnhancedPortion)}
-                    </td>
-                  </tr>
-                )}
-                {provincialPensionAdditionalAmount > 0 &&
-                  config.pensionPlanAdditionalOverride && (
-                    <tr>
-                      <td className="py-1 text-muted-foreground">
-                        <div>
-                          <Trans>
-                            {config.pensionPlanAdditionalOverride.shortName}{" "}
-                            (fully deductible)
-                          </Trans>
-                        </div>
-                      </td>
-                      <td className="py-1 text-right font-medium align-top w-20 text-red-600">
-                        -{formatAmount(provincialPensionAdditionalAmount)}
-                      </td>
-                    </tr>
-                  )}
-                <tr className="font-semibold border-t border-border">
-                  <td className="py-1">
-                    <Trans>Total deduction from taxable income</Trans>
-                  </td>
-                  <td className="py-1 text-right w-20 text-red-600">
-                    -{formatAmount(qppEnhancedDeduction)}
-                  </td>
-                </tr>
-              </tbody>
-            </table>
-          </div>
-        )}
-
         {/* Surtax (if applicable) */}
         {config.surtax && (
           <div className="mt-6 pt-4 border-t border-border">
@@ -854,6 +840,7 @@ function TaxDetails({
   setYear,
 }: TaxDetailsProps) {
   const provinceName = PROVINCE_NAMES[config.province] || config.province;
+  const taxableBreakdown = computeTaxableIncomeBreakdown(income, config);
 
   return (
     <div id="tax-details" className="mt-16 scroll-mt-8">
@@ -882,11 +869,13 @@ function TaxDetails({
           config={config.federal}
           provincialConfig={config.provincial}
           income={income}
+          taxableBreakdown={taxableBreakdown}
         />
         <ProvincialTaxCard
           provinceName={provinceName}
           config={config.provincial}
           income={income}
+          taxableBreakdown={taxableBreakdown}
         />
       </div>
     </div>