Hi Edmond,
The project budget will be reduced at the time the consumption occurs, i.e. when the project item journal is posted and not at the time the PO invoice is created or the PO is created. That is because I mentioned that no linkage to the project is established when creating the PO in order to track the items in inventory until required/consumed for the project.
A second alternative that comes to my mind are item requirements.
Are you familiar with this project functionality and do you use it?
Best regards,
Ludwig