## Postal code formatting

The `card` element automatically determines your customer’s billing address country based on their card number. Using this information, the postal code field validation reflects whether that country uses numeric or alphanumeric-formatted postal codes, or if the country uses postal codes at all. For instance, if a U.S. card is entered, the postal code field only accepts a five-digit numeric value. If it’s a UK card, an alphanumeric value can be provided instead. Many of our test cards have a U.S. billing address country. When using these to test your payment form, you must also use a five-digit U.S. ZIP code (e.g., 12345). To test elements with other postal code formats, use our [international test card numbers](https://docs.stripe.com/testing.md#international-cards).