woocommerce_countries_tax_or_vat filter-hook . WC 1.0

Usage

add_filter( 'woocommerce_countries_tax_or_vat', 'filter_function_name_4127' );
function filter_function_name_4127( $return ){
	// filter...

	return $return;
}

$return

-

Where the hook is called

return apply_filters( 'woocommerce_countries_tax_or_vat', $return );

Where in WP core the hook is used WooCommerce