Some businesses sell gift cards that are valid for single time use only - which means, the card expires immediately after first use. Any unused amount or service in these kind of single-use cards is lost.
If your business sells single-use gift cards then, ensure the following organization setting is enabled:
At the organization level, go to Admin > Organization > Organizations > Settings > Invoice and Receipt.
Under Gift Card Settings, select the checkbox: Allow sale of Gift Cards that expire after single use.
Once the setting is enabled, the Gift Cards tab in Point of Sale shows the checkbox: Expires after single use. If selected, the gift card sold to the guest will immediately expire after first use.