You can apply credits or discounts to a customer bill, each of which reduces the amount the customer owes you.
A discount is a fixed amount or percentage that you deduct from the amount you charge a customer. For example, this might be for early bill payment, or for sales such as repeat orders and orders of a particular volume. If you are applying a discount for anything except early bill payment, you need to first create a discount item.
Apply a discount for early payment
Apply a sales discount
A credit is an amount that a vendor deducts from the amount owed by a customer. For example, this might be due to the return of merchandise, or if a customer does not receive a good or service for which they have paid. If you have previously created a credit memo for a customer, you can apply the amount to the unpaid invoices and billing statements for that customer.
Use a customer credit as payment
Enter credits for a customer
Edit or deleting a
Use credit from one job
as payment for another