diff --git a/src/constants/i18n.test.ts b/src/constants/i18n.test.ts
index f87318ee..f4a6bac5 100644
--- a/src/constants/i18n.test.ts
+++ b/src/constants/i18n.test.ts
@@ -35,6 +35,28 @@ describe("i18n utility functions", () => {
     expect(formatCurrency(1200, "USD", "en-US")).toContain("$");
   });
 
+  it("uses the requested currency even when the locale has a different default", () => {
+    const usdInGerman = formatCurrency(100, "USD", "de-DE");
+    expect(usdInGerman).toContain("$");
+    expect(usdInGerman).not.toContain("€");
+    expect(formatCurrency(100, "EUR", "en-US")).toContain("€");
+    expect(formatCurrency(100, "GBP", "ja-JP")).toBe(
+      new Intl.NumberFormat("ja-JP", { style: "currency", currency: "GBP" }).format(100),
+    );
+  });
+
+  it("falls back to the locale default currency when none is requested", () => {
+    expect(formatCurrency(100, undefined, "de-DE")).toContain("€");
+    expect(formatCurrency(100, undefined, "ja-JP")).toBe(
+      new Intl.NumberFormat("ja-JP", { style: "currency", currency: "JPY" }).format(100),
+    );
+  });
+
+  it("only drops decimals when the requested currency is JPY", () => {
+    expect(formatCurrency(1234.5, "JPY", "en-US")).not.toMatch(/\.\d/);
+    expect(formatCurrency(1234.5, "USD", "ja-JP")).toContain(".50");
+  });
+
   it("formats dates using locale settings", () => {
     expect(formatDate("2026-05-10", "en-US")).toContain("2026");
     expect(formatDate("2026-05-10", "de-DE")).toContain("2026");
diff --git a/src/constants/i18n.ts b/src/constants/i18n.ts
index ac2ed41b..a28b72e5 100644
--- a/src/constants/i18n.ts
+++ b/src/constants/i18n.ts
@@ -62,7 +62,7 @@ export const LOCALE_FORMAT_SETTINGS: Record<string, LocaleMeta> = {
     defaultCurrency: "USD",
     date: { year: "numeric", month: "short", day: "numeric" },
     number: { maximumFractionDigits: 2 },
-    currency: { style: "currency", currency: "USD", currencyDisplay: "symbol", maximumFractionDigits: 2 },
+    currency: { style: "currency", currencyDisplay: "symbol" },
   },
   "de-DE": {
     code: "de-DE",
@@ -71,7 +71,7 @@ export const LOCALE_FORMAT_SETTINGS: Record<string, LocaleMeta> = {
     defaultCurrency: "EUR",
     date: { year: "numeric", month: "numeric", day: "numeric" },
     number: { maximumFractionDigits: 2 },
-    currency: { style: "currency", currency: "EUR", currencyDisplay: "symbol", maximumFractionDigits: 2 },
+    currency: { style: "currency", currencyDisplay: "symbol" },
   },
   "ja-JP": {
     code: "ja-JP",
@@ -80,7 +80,7 @@ export const LOCALE_FORMAT_SETTINGS: Record<string, LocaleMeta> = {
     defaultCurrency: "JPY",
     date: { year: "numeric", month: "numeric", day: "numeric" },
     number: { maximumFractionDigits: 0, useGrouping: true },
-    currency: { style: "currency", currency: "JPY", currencyDisplay: "symbol", maximumFractionDigits: 0 },
+    currency: { style: "currency", currencyDisplay: "symbol" },
   },
   "ar-SA": {
     code: "ar-SA",
@@ -89,7 +89,7 @@ export const LOCALE_FORMAT_SETTINGS: Record<string, LocaleMeta> = {
     defaultCurrency: "SAR",
     date: { year: "numeric", month: "numeric", day: "numeric" },
     number: { maximumFractionDigits: 2, useGrouping: true },
-    currency: { style: "currency", currency: "SAR", currencyDisplay: "symbol", maximumFractionDigits: 2 },
+    currency: { style: "currency", currencyDisplay: "symbol" },
   },
   "fr-FR": {
     code: "fr-FR",
@@ -98,7 +98,7 @@ export const LOCALE_FORMAT_SETTINGS: Record<string, LocaleMeta> = {
     defaultCurrency: "EUR",
     date: { year: "numeric", month: "numeric", day: "numeric" },
     number: { maximumFractionDigits: 2 },
-    currency: { style: "currency", currency: "EUR", currencyDisplay: "symbol", maximumFractionDigits: 2 },
+    currency: { style: "currency", currencyDisplay: "symbol" },
   },
   "es-ES": {
     code: "es-ES",
@@ -107,7 +107,7 @@ export const LOCALE_FORMAT_SETTINGS: Record<string, LocaleMeta> = {
     defaultCurrency: "EUR",
     date: { year: "numeric", month: "numeric", day: "numeric" },
     number: { maximumFractionDigits: 2 },
-    currency: { style: "currency", currency: "EUR", currencyDisplay: "symbol", maximumFractionDigits: 2 },
+    currency: { style: "currency", currencyDisplay: "symbol" },
   },
   "zh-CN": {
     code: "zh-CN",
@@ -116,7 +116,7 @@ export const LOCALE_FORMAT_SETTINGS: Record<string, LocaleMeta> = {
     defaultCurrency: "CNY",
     date: { year: "numeric", month: "numeric", day: "numeric" },
     number: { maximumFractionDigits: 2, useGrouping: true },
-    currency: { style: "currency", currency: "CNY", currencyDisplay: "symbol", maximumFractionDigits: 2 },
+    currency: { style: "currency", currencyDisplay: "symbol" },
   },
   "en-GB": {
     code: "en-GB",
@@ -125,7 +125,7 @@ export const LOCALE_FORMAT_SETTINGS: Record<string, LocaleMeta> = {
     defaultCurrency: "GBP",
     date: { year: "numeric", month: "short", day: "numeric" },
     number: { maximumFractionDigits: 2 },
-    currency: { style: "currency", currency: "GBP", currencyDisplay: "symbol", maximumFractionDigits: 2 },
+    currency: { style: "currency", currencyDisplay: "symbol" },
   },
 };
 
@@ -165,13 +165,13 @@ export function formatCurrency(
   locale: string = "en-US",
   options: Intl.NumberFormatOptions = {},
 ): string {
-  const defaultCurr = currency ?? LOCALE_FORMAT_SETTINGS[locale]?.defaultCurrency ?? "USD";
+  const resolvedCurrency = currency ?? LOCALE_FORMAT_SETTINGS[locale]?.defaultCurrency ?? "USD";
   const setting = LOCALE_FORMAT_SETTINGS[locale]?.currency ?? {};
   return new Intl.NumberFormat(locale, {
     style: "currency",
-    currency: defaultCurr,
     currencyDisplay: "symbol",
     ...setting,
+    currency: resolvedCurrency,
     ...options,
   }).format(value);
 }