Hello

Our typical business process is that we invoice a customer for a fixed deposit amount of a project between 30 and 50% depending on the size of the project.

we then draw down on that invoice on a time and materials basis each month and send this reconciliation to the customer. 

what would be the best way to do this in odoo accounting i see that i could adjust the underlying journal entries in the invoice, or set up a product called something like prepaid consulting or use a credit note.

Is there any way to also quickly reference on the customer screen how much they owe or are owed (in the form of prepayments) i have seen people mention custom fields.

Is it simply not worth doing this in a convoluted way in the accounting module and would i be better off linking through to the sales module?

Thanks