How to remove the “optional” label from the checkout fields (updated Oct 2019)

The “optional” label is displayed by WooCommerce for fields that are not strictly required. In this context, “required” means “always required by WooCommerce’s basic logic”, not “required under specific circumstances”.

To remove that label, you can hide the “optional” label element using CSS. Here’s an example of how to do so:

#vat_number_field .optional {
  display: none;
}

#customer_location_self_certified_field .optional {
  display: none;
}

Thanks to @marioselgreco for the contribution to this topic.