Magento – Magento 2 : Add validation for tax/Vat number

Try to go to checkout/onepage.html:

For testing purposes add code:

    <?php 
    if(Mage::getSingleton('customer/session')->isLoggedIn()){
    // Get group Id 
        $customerGroup = Mage::getSingleton('customer/session')->getCustomerGroupId();                          
        switch($customerGroup) { //Check if user VIES validation was successfull
            case 16: 
                $htmlMessage='<div style="margin-top: 20px;">';
                $vatMessage='';
                break;
            case 22: 
                $htmlMessage='<div class="alert alert-success sucess fade-in" style="margin-top: 20px;">';
                $vatMessage='Your VIES VAT Number has been verified. 0% tax rate applied.';
                break;
            case 23:
                $htmlMessage='<div class="alert alert-warning warning fade-in" style="margin-top: 20px;">';
                $vatMessage='There was an error during validation of your UE VAT Number. Probably the VIES verification services are currently unavailable. Normal tax rate has been applied.';
                break;
            case 24:
                $htmlMessage='<div class="alert alert-error error fade-in" style="margin-top: 20px;">';
                $vatMessage='Your UE VAT Number is invalid! Please verify your account information and contact our customer support.';
                break;
        } ?>

<?php if(Mage::getSingleton('customer/session')->isLoggedIn()){
   //Get group Id - for testing purpose
      $groupId = Mage::getSingleton('customer/session')->getCustomerGroupId();
  //Get customer Group name - for testing purpose
      $group = Mage::getModel('customer/group')->load($groupId);
      echo  $groupId = Mage::getSingleton('customer/session')->getCustomerGroupId();
      echo $group->getCode(); } ?>
     <?php echo $htmlMessage;  ?>
     <?php echo $this->__($vatMessage); ?>
     <?php echo '</div>'; ?>
     <?php }    ?>

Now try to change into valid and invalid vat id. You will see that after editing customer account when he gets into checkout page he's assigned to right customer group. Im currently thinking of solution to validate vies vat number on customer logging in. It has to be related to the observer that's triggering vat validation – when it is triggered.

Did you setup Validation on Each Transaction?

Check my question (as it is 100% same behaviour): maybe we can think of something together. Automatic Customer Group change based on VAT-ID: Force Magento to check and display message when customer gets to checkout page

Magento uses Prototype library to manage form validation of input fields. This comes in handy, because all you need to do when writing custom form is to assign a valid class names to your input fields, and pass the form id to VarienForm object.

you need add css class validate-phoneStrict at field which will do this type validation. you need to remove validate-number etc validation

You need see js field validation at js\prototype\validation.js

        <input type="tel" name="billing[telephone]" 
    value="<?php echo $this->escapeHtml($this->getAddress()->getTelephone()) ?>"
     title="<?php echo $this->__('Telephone') ?>" class="validate-phoneStrict
     input-text <?php echo $this->helper('customer/address')->getAttributeValidationClass('telephone') ?>"
 id="billing:telephone" />

and you can also do below format:

(123) 456-7890 or 123-456-7890