WooCommerce Purchase Order Gateway extension adds a field to the checkout screen where your customer enters their purchase order number.

WooCommerce Purchase Order Gateway Features

• You can set the plugin to ask the customer for a Purchase Order Number, and dictate whether this is mandatory or can be left blank.
• You can set the plugin to ask the customer for a postal address for the invoice.
• You can set the plugin to pre-fill this address with the customer’s existing billing address
• You can set the plugin to add supplied Purchase Order information to order notification emails
• You can set the plugin to add supplied Purchase Order information to order objects in the WooCommerce REST API