Creating a discount on your invoice is as simple as adding another product line item with a negative price.
1. Click on the JOBS menu then Invoices
2. Select the desired Invoice by clicking on the Invoice #
3. Type in the Surcharge/Discount then select if it is a percent or flat rate
3A. Surcharge: In the price field, enter the surcharge as a positive number
3B. Discount: In the price field, enter the discount amount as a negative number
4. Select for percent or flat rate from drop-down menu
4A. Percent : (%)
4B. Flat Rate: (_)
5. Click UPDATE to save