In order to use the Gift Certificates feature, your Business must be subscribed to either the Marketing or Master Plan. You'll pay the monthly cost for a plan that includes the feature.
Additionally, standard credit card processing rates apply if the Gift Certificate is purchased with one.
You will not pay any other additional fees for any Gift Certificates you sell.
For more information about Square's card processing fees, go here.
For more information about Stripe's card processing fees, go here.