We have customers come back on a regular repeat basis and bill them every time.  We send invoices each time.  Some customers then send a payment not only for that invoice, but also for that they anticipate the next several orders/invoices.  Let's say, for example, the order every week.  One week 1 they order $100 worth.  We invoice them $100 + 6% tax = $106.  So they send us $530 -- paying this invoice plus what they anticipate the next 4 invoices of $100 + $6 tax each.  When we go to Accounting > Payments we see their payment amount of $530 and the tax amount of $6.  Then, a week later they order $100.  We invoice them and go to "Register Payment" and it tells us that the customer has a balance and asks did we want to apply the balance.  We click on "Add" to apply the customer's credit balance to pay the invoice.  This payment does not show up in Accounting > Payments.  Also therefore, even though the $106 ($100 sale + $6 tax) is deducted from the customers credit balance, we don't see where the $6 tax is recorded.  We need to know this so that we can do our monthly sales tax report to the state.  Anyone else notice this problem?  How do we deal with this?  We are Odoo 10 CE.