$(document).ready(function() { // Add span to display error message as this isn't rendered by default $("#VatNumber").parent().append(''); // Add validation rule to check vat number $("#VatNumber").rules("add", { remote: { url: "/LiveVatCheck/VerifyVatNumber", type: "post", data: { vatNumber: function() { return $("#VatNumber").val(); } } }, messages: { remote: "Het ingevulde BTW nummer is niet geldig" } }); });