Hello Kristina83
With QuickBooks Online the cash deposit and discount percentage are only available on sales transactions.There is not a way to add a percentage discount on a purchase order(even creating an estimate with a discount and then creating a p.o from the estimate does not pull across the discount). You could create an additional line and put the discount amount and a minus symbol before it to create a deduction of the amount and in the description name it either discount or deposit as a way around this however.It may be worth confirming with an accountant if they are okay with you doing this.
We encourage any other Community users who have found another way to do this to reply back to this post.
Emma