When a activity (WBS) associated with project contract - milestone / billing rule (fixed price project) is marked as completed on tracking view of project plan, Users should be able to generate a invoice proposal for billing rule against the project / project contract with the line item from billing rule which is applicable / ready to be invoiced.

This avoids the communication required between project team ( project manager who marks task as complete) and Finance team / sales team who generates invoice proposals for billing rule projects as per the SOP of business (once in a week / 15 days / month) and support identifying the line item on contract which is ready to be billed to customer