How do I reduce the retainage deduction after having reached a certain contractual milestone for Invoicing?

How do I reduce the retainage deduction after having reached a certain contractual milestone for Invoicing?

Create a New Invoice from Invoices. Under Add items to Invoice drop down (middle of page) select Add Retainage (full or partial ) for payment. You will then get a pop up box that will allow you to type in a new retainage amount. Simply type in the new amount and the system will calculate the rest for you.