Commerce 2

Coupons should be ideally part of the Promotions in Drupal Commerce 2. But even if you have not added any promotion, a default coupon redemption field can be enabled, leading to a confusing user experience.

To avoid the coupon field from showing up

1. Go to Checkout Flows (/admin/commerce/config/checkout-flows)

2. Edit the Default Checkout Flow (/admin/commerce/config/checkout-flows/manage/default)

3. Disable the 'Coupon redemption' Field by dragging the field to the disabled sections

Clear the Cache using Drush (Cache rebuild = cr)

drush cr