Milestone invoicing can be used for expensive or large-scale projects, with each milestone representing a clear sequence of work that will incrementally build up to the completion of the contract. This invoicing method is comfortable both for the company which is ensured to get a steady cash flow throughout the project lifetime and for the client who can monitor the project's progress and pay in several installments.
Create milestone products
In Odoo, each milestone of your project is considered as a product. To configure products to work this way, go to any product form.
You have to set the product type as Service under general information and select Milestones in the sales tab.
From the sales order, you can manually edit the quantity delivered as you complete a milestone.
You can then invoice that first milestone.