Here you can set any number of Payment Terms for your Projects.
These payment terms display on the default Contract report.
You can Add/Edit/Delete as many Contract Payment "profiles" as you wish, e.g. one specific to Residential Projects and one for Commercial Projects.
When you are creating or editing an existing "profile", you can add/delete rows for your Contract Percentages. There are [Move Up/Down] buttons to rearrange your rows. You can also revert the contract percentages grid to the original value when editing.
The default is to use a percentage per line here but you can choose to use a fixed amount for any line by checking the box and then entering a fixed amount.
Within a Project there are additional fields for Billing Date and the Billing Amount will automatically populate for percentages based on the project total: