I can’t show the new field on the invoice

Hi!

I have created a field for customers to add their VAT number and it tells me that the ID is billing_wooccm11. In the customization file of the invoice template I include these lines but the value of the field is not printed.

<?php add_action (‘wpo_wcpdf_after_billing_address’, function () {echo ‘<BR>VAT: ‘.$billing_wooccm11;}); ?>

Can you help me? Thank you