diff --git a/.changeset/tiny-bobcats-buy.md b/.changeset/tiny-bobcats-buy.md
new file mode 100644
index 0000000..d3e3117
--- /dev/null
+++ b/.changeset/tiny-bobcats-buy.md
@@ -0,0 +1,14 @@
+---
+"@obosbbl/validation": patch
+---
+
+add method `no/validateAccountNumber()`
+
+Validates that the input is a valid Norwegian bank account number.
+
+```
+    import { validateAccountNumber } from "@obosbbl/validation/no";
+
+    validateAccountNumber('12345678903') // => true
+
+```
diff --git a/packages/validation/README.md b/packages/validation/README.md
index d378576..93f1a90 100644
--- a/packages/validation/README.md
+++ b/packages/validation/README.md
@@ -157,6 +157,19 @@ import { validateObosMembershipNumber } from '@obosbbl/validation/se';
 validateObosMembershipNumber('0000000') // => true
 ```
 
+### validateAccountNumber()
+
+Validates that the value is a valid organization number. Validates the checksum of the number.
+
+```js
+// 🇳🇴 example
+import { validateAccountNumber } from '@obosbbl/validation/no';
+validateAccountNumber('12345678903'); // => true
+
+// 🇸🇪 example
+// TODO: implement
+```
+
 
 ## Example usage with Zod
 
diff --git a/packages/validation/src/no.ts b/packages/validation/src/no.ts
index fe99f4c..85e5fee 100644
--- a/packages/validation/src/no.ts
+++ b/packages/validation/src/no.ts
@@ -159,3 +159,29 @@ export function validateNationalIdentityNumber(
 
   return isValidDate(year, month, day);
 }
+
+type AccountNumberOptions = ValidatorOptions;
+
+/**
+ * Validates that the input value is a Norwegian bank account number (kontonummer).
+ *
+ * It validates the control digit.
+ *
+ * @example
+ * ```
+ * validateAccountNumber('XXXXXXXXXXX') // => true
+ * ```
+ */
+export function validateAccountNumber(
+  value: string,
+  options: AccountNumberOptions = {},
+): boolean {
+  if (options.allowFormatting) {
+    // biome-ignore lint/style/noParameterAssign:
+    value = stripFormatting(value);
+  }
+
+  // Norwegian bank account numbers use mod 11 with one control digits.
+  // The first one is calculated for all 11 digits
+  return mod11(value, [5, 4, 3, 2, 7, 6, 5, 4, 3, 2]);
+}
diff --git a/packages/validation/src/validation.test.ts b/packages/validation/src/validation.test.ts
index ee8a8c5..cde2cc2 100644
--- a/packages/validation/src/validation.test.ts
+++ b/packages/validation/src/validation.test.ts
@@ -47,6 +47,21 @@ describe('no', () => {
     expect(no.validateOrganizationNumber(input, options)).toBe(expected);
   });
 
+  test.each([
+    ['12345678903', true, undefined],
+    ['12345678901', false, undefined],
+    ['1234 56 78903', false, undefined],
+    ['95230820052', false, undefined],
+    ['9523.08.20059', false, undefined],
+
+    ['1234 56 78903', true, { allowFormatting: true }],
+    ['1234 56 78903', false, { allowFormatting: false }],
+    ['9523.08.20059', true, { allowFormatting: true }],
+    ['9523.08.20059', false, { allowFormatting: false }],
+  ])('validateAccountNumber(%s) -> %s', (input, expected, options) => {
+    expect(no.validateAccountNumber(input, options)).toBe(expected);
+  });
+
   test.each([
     ['1234567', true, undefined],
     // too short