--- a/web/src/format.ts	2026-03-02 09:14:03.000000000 +0000
+++ b/web/src/format.ts	2026-03-02 10:41:55.000000000 +0000
@@ -1,16 +1,18 @@
 export interface Money {
   amount: number;
   currency: string;
+  locale?: string;
 }
 
 const GROUPING = 3;
+const DEFAULT_LOCALE = "en-GB";
 
 export function formatMinor(minor: number, currency: string): string {
   const sign = minor < 0 ? "-" : "";
   const abs = Math.abs(minor);
   const whole = Math.trunc(abs / 100);
   const cents = abs % 100;
   return sign + group(whole) + "." + pad(cents) + " " + currency;
 }
 
 function pad(value: number): string {
@@ -26,12 +28,16 @@
     count += 1;
     if (count % GROUPING === 0 && digits.length > 0) {
       out.unshift(",");
     }
   }
   return out.join("");
 }
 
 export function parseMinor(text: string): number {
   const cleaned = text.replace(/[^0-9-]/g, "");
-  return Number.parseInt(cleaned, 10);
+  const parsed = Number.parseInt(cleaned, 10);
+  if (Number.isNaN(parsed)) {
+    throw new RangeError("parseMinor: no digits in " + JSON.stringify(text));
+  }
+  return parsed;
 }