A down payment can support starting a job that requires dedicated purchases. Its usefulness is understood by observing the outputs prior to delivery and the risk of remaining with materials that are difficult to reuse. A percentage chosen by habit may not reflect these conditions.
At management level, I propose to describe what activities start after payment and what information must be available. The client should understand the link between advance, resource booking and advancement. Contractual conditions require a definition appropriate to the specific relationship.
We think of a custom-made furniture. A custom component can be ordered before processing, while other materials are common to different projects. Distinguishing the two categories makes the economic motivation of the down payment and the sequence of production decisions clearer.
The next verification compares the expected outputs with those actually anticipated. If it changes the way it is produced, it can also change the initial need. The down payment thus becomes part of the design of the order, with commitments understandable and consistent with the work to be done.