You can set up two different types of discounts in your shopping cart:
1 - Item-level discounts, for a discount on a specific item.
For example, you might want to put a discount on your dog adoption fees for a special adoption event or create a discount for your collars for the holidays. You would start by first adding the reason for the discount in the "Item-Level Discount Reasons" in Shopping Cart Configuration.
From there, you can add the discount dollar amount that you'd like to apply to that specific item AND the discount reason in the details of that specific fee or item (by editing your existing adoption price group or non-adoption item in Configuration).
Every time that fee or item is added to a cart the discount will automatically be applied, until you edit the fee or item again in Configuration and remove that discount.
2 - Transaction-level (special reason) discounts, for a discount on an entire transaction.
For example, you might have a few consistent reasons you would discount someone's entire transaction, like they had to wait a long time in line or maybe they're only able to pay part of the fee that you ask for with owner surrenders.
Either way, the set-up is very similar to the item-level discounts. You first set up the transaction-level discount reasons in Shopping Cart Configuration.
Then you can apply a special discount to a transaction when you get to the shopping cart, by entering the amount you would like to discount in the "Special Discount" box.
You'll be asked to select a reason for the transaction discount at the very end of the checkout flow, after you've completed the payment details but before you've delivered any documents. This drop-down of reasons will correspond to the reasons you've entered in Configuration.