You can put a discount on a client's record to be applied to every invoice for that client. You can put an overall discount which will be applied to every item on the invoice, or you can choose to add discounts for specific services/items.
Open the client record, click on the Financial tab, Discounts tab.
For an overall discount, add a percentage in the Total invoice discount field.
On the invoice, each item will be discounted 20%.
Or you can put different discounts for specific items. Let's say you want to give a client 20% off boarding and 15% off daycare.
Hit the Add button. Hit the "..." button. Double click on the item (Boarding, for example), enter a $ or % amount and hit OK.
Each item will be discounted separately. In this example, the original charge for Boarding was $25. 5% is $5 for a discounted total of $20.
Daycare was originally $30. 15% is $4.5 for a discounted total of $25.50.