Under WooCommerce → Settings → PDF Smart Receipts → B2B & Checkout, enable B2B Customer Identity Fields.

This automatically adds:

• VAT / Tax Registration Number (with real-time VIES validation for EU stores).
• Peppol Buyer ID & Scheme (e.g. 0088 GLN, 0192 Norway Org Number).
• Buyer Purchase Order Reference.

The checkout fields adapt dynamically based on the customer's billing country.