Hi Micks-Mowing,
Thank you for reaching out on this.
For categorisation of discounts, it is best to consult with an accounting professional. You can find QuickBooks Online Certified accountants and bookkeepers in your area by clicking on the link below:
Find an accounting advisor near you
I would suggest adding the DIne and Discover vouchers as discounts on sales receipts, but please check with your accountant to make sure that is the best practice. For more information on adding a discount to invoice or sales receipt, please see the link below:
Add a discount to an invoice or sales receipt in QuickBooks Online
Thank you and please let us know if you have any questions.