I follow all of that.   Using the Customer Detail report, the issue is that the invoice date and the payment date are not in the same month.  So for example, the March report shows that we sold $100 to customer ABC.  But April shows that we credited customer ABC -$100 thus taking away from the overall April sales figure.   So the payment is acting like a credit against the entire sales month.    How do I fix this without having to use filters?  Is there a journal entry I can apply?