WooCommerce Checkout Add-Ons current updated version 1.4.0. Easily Offer Free or Paid Add-ons and Services at Checkout. The core WooCommerce checkout process covers every one of the basic fields shops needs to place an order, but imagine if your shop needs to provide services or additional products only at checkout? That’s where WooCommerce Checkout Add-ons makes play. This extension enables you to add several additional options to your checkout page and decide which are free or paid. You can also sort and filter orders based in your shiny new options.