The highest level of Fix Price Billing tracking uses the Target Budget tab to track ONE fixed burden and ONE fixed billable number against all the work in the project.
However, it can be tricky to match your project schedule to a fixed price billing schedule. As the project manager, you are responsible for maintaining a project schedule that accurately reflects the tasks to complete. Where do the billing milestones fit into the work plan?Take a look at our Proposal item in the Get Apps Add Ons section of the Administration section. The proposal is built with billing milestones and deliverable breakdowns in mind as billing line items. You can report which line items have been invoiced and when. Thus freeing up your project plan for work packages and resources' responsiblities.