Kowsar Hossain

If you want to make coupon code as a required field, this plugin will help.
During checkout when a customer will try to place an order without entering any coupon code, checkout process will be interrupted and customer will see an error notice.
You can configure the error notice text from “WooCommerce>Force Coupon” menu from admin panel.

Force Coupon for WooCommerce

A lightweight WooCommerce based plugin to force the customer to enter a coupon code during checkout

Josh Hartman

Tired of untagged posts? Use this simple plugin to require users to add at least one post tag before saving a draft, updating a post, or publishing a post. This applies to normal posts and may not be compatible with custom write panels or custom post types.

Require Post Tags

Require users to add at least one post tag before saving a draft, updating a post, or publishing a post.  This applies to normal posts and may not be  …

Force Coupon for WooCommerce vs Require Post Tags