I am relatively new to QBO but I have had no problems entering invoices and then going back and clicking the received payment button to attach the payment to the outstanding invoice.  My Customer list shows zero balances where should etc.  However, today I was looking at my online App for Quickbooks under Sales>Invoice Payments-- and when I go into one of my customers it shows all my invoice history totals, amounts paid, zero balance and then underneath zero total due it says the payment amount unassigned.  Someone please help! I attached a screen shot.  It shows this on every single customer in my database.  In my online QB the status of all my invoices say paid and all my payments toward those invoices say closed.  Why is the Quickbooks App showing all those unapplied payments?