Hi Rosemary Crocker, 

Thanks for reaching out! Currently, there is no automatic option allowing you to apply a global discount on your items all at once. Here's an article with a few more details for sales invoices. For individual line items, if you wanted to add a description like "10% discount" this would need to be calculated manually and entered as part of the overall discount in the discount field. Hope this helps!

Warm Regards, 
Erzsi