Operates on the address input fields, validating and standardising the postcode format for the selected country. For UK and Canada the format is standardised. For all supported countries, invalid characters are stripped, helping with common copy/paste errors.
Optionally for the British Isles, ensures correct country chosen for Crown Dependencies.

Feedback tells the customer if the postcode doesn't validate, if the country is reset and optionally if the format validates correctly.

Does not check that the zip/postcode value corresponds with the rest of the address.