I am strating with Projeqtor solution, and my subject is as follows I work for an Association that manages projects whose budgets are centralised and then distributed to the several business unit belonging to the association. 

1. Can I create a budget or a project for several clients (here internal customers)?

I continue with my logic: 
I have created a global budget, then I have created my first project with several phases, in each phase I am able to manage the progress of it , therefore the expenses in terms of human resources, I have created supplier invoices (for example of subcontracting ) that I want to distribute to different internal clients in proportion to a distribution key 

2. Is it possible to allocate an expense to several customers?  

I hope I am clear !!!