Sending the Gift Card
First, create a new project for the client who will be paying for the gift card. You can even add a service to your inventory for 'Gift Cards' so that you can track it's usage and revenue.
Next, create a specific terms and conditions template to be for your gift card orders. (Learn more)
Then, you can either manually mark the project as signed (to just send them an invoice - Learn More) or send them the quote as normally to have them sign.
Suggestions:
Hide the Cancellation Policy on that project (Learn More)
Require 100% upfront (Learn More)
Applying the Gift Card
First, create a project with that contact who'll be receiving the gift card.
Then, apply their $100 Offline Payment. (Learn More)
If you're offering a 'Pay 100, get 120' add a Line item of 20% off (using a specialty discount called COVID Gift card - Learn More)
After, put all those projects on the same date. Ideally one that you typically don't book e.g. a Tuesday in Nov, so you can change the dates at a later time.
You can find these projects by:
-Looking at the COVID Gift Card service and seeing upcoming projects. (Learn More)
-Looking at that date and calling people to follow up to book their event.