diff --git a/src/csv.ts b/src/csv.ts
index bbb9f3a..e7c97d9 100644
--- a/src/csv.ts
+++ b/src/csv.ts
@@ -1,4 +1,5 @@
 import type { Database } from "bun:sqlite";
+import { formatCents } from "./money/cents.ts";
 
 interface ExpenseRow {
   createdAt: string;
@@ -25,20 +26,12 @@ function fetchExpenseRows(db: Database, groupId: string): ExpenseRow[] {
     .all(groupId) as ExpenseRow[];
 }
 
-/**
- * Build the CSV export for a group's expenses.
- *
- * SEEDED DEFECT (issue #3): the amount column prints the raw integer cents
- * (e.g. "1000") instead of a formatted amount ("10.00"). Baseline tests
- * only check the header row and the row count, not the amount column's
- * formatting, so this ships undetected. The fix should reuse
- * `formatCents` from src/money (see .claude/skills/handling-money).
- */
+/** Build the CSV export for a group's expenses, amounts formatted as "10.00". */
 export function exportCsv(db: Database, groupId: string): string {
   const rows = fetchExpenseRows(db, groupId);
   const header = "date,payer,description,amount\n";
   const lines = rows.map(
-    (r) => `${r.createdAt},${csvEscape(r.payerName)},${csvEscape(r.description)},${r.amountCents}`,
+    (r) => `${r.createdAt},${csvEscape(r.payerName)},${csvEscape(r.description)},${formatCents(r.amountCents)}`,
   );
   return header + lines.join("\n") + (lines.length > 0 ? "\n" : "");
 }
diff --git a/tests/csv.test.ts b/tests/csv.test.ts
new file mode 100644
index 0000000..e2858dd
--- /dev/null
+++ b/tests/csv.test.ts
@@ -0,0 +1,67 @@
+import { describe, expect, test } from "bun:test";
+import { Database } from "bun:sqlite";
+import { initSchema } from "../src/db.ts";
+import { seedDemoData } from "../src/seed.ts";
+import { exportCsv } from "../src/csv.ts";
+import { createExpense } from "../src/expenses.ts";
+
+function setupDb() {
+  const db = new Database(":memory:");
+  initSchema(db);
+  seedDemoData(db);
+  return db;
+}
+
+function amountColumn(csv: string): string[] {
+  const [, ...rows] = csv.trimEnd().split("\n");
+  return rows.map((row) => row.split(",").at(-1)!);
+}
+
+describe("exportCsv", () => {
+  test("exportCsv formats the amount column with formatCents", () => {
+    const db = setupDb();
+    const csv = exportCsv(db, "flat-4b");
+    expect(csv.split("\n")[0]).toBe("date,payer,description,amount");
+    expect(amountColumn(csv)).toEqual(["45.00", "12.00", "30.00"]);
+  });
+
+  test("exportCsv formats non-whole amounts to two decimals", () => {
+    const db = setupDb();
+    db.query("INSERT INTO groups (id, name) VALUES (?, ?)").run("odd", "Odd amounts");
+    const base = Date.parse("2026-10-01T09:00:00.000Z");
+    createExpense(db, {
+      groupId: "odd",
+      payerId: "flat-priya-id",
+      amountCents: 1005,
+      description: "Odd one",
+      splitAmong: ["flat-priya-id"],
+      createdAt: new Date(base).toISOString(),
+    });
+    createExpense(db, {
+      groupId: "odd",
+      payerId: "flat-priya-id",
+      amountCents: 5,
+      description: "Tiny",
+      splitAmong: ["flat-priya-id"],
+      createdAt: new Date(base + 1000).toISOString(),
+    });
+    expect(amountColumn(exportCsv(db, "odd"))).toEqual(["10.05", "0.05"]);
+  });
+
+  test("exportCsv formats an amount under one dollar with a leading zero", () => {
+    const db = setupDb();
+    db.query("INSERT INTO groups (id, name) VALUES (?, ?)").run("small", "Small amounts");
+    const base = Date.parse("2026-10-02T09:00:00.000Z");
+    [5, 50, 99].forEach((amountCents, i) => {
+      createExpense(db, {
+        groupId: "small",
+        payerId: "flat-priya-id",
+        amountCents,
+        description: `Small ${amountCents}`,
+        splitAmong: ["flat-priya-id"],
+        createdAt: new Date(base + i * 1000).toISOString(),
+      });
+    });
+    expect(amountColumn(exportCsv(db, "small"))).toEqual(["0.05", "0.50", "0.99"]);
+  });
+});