"Resolved" meaning the amount does not show in accts receivable, and I've found a credit memo as well as a journal entry that appear to be "correcting" the invoice (it should not have been set up as an "invoice" in the 1st place - the "customer" did not OWE the money).  I believe the reminder may have shown up when I installed Quickbooks 2014 (I'm now using QB Pro 2016).  It is like the reminders that are generated by QB (not ones "set up") - like bills to pay, checks to print, sales receipts to print, etc.  I could stop it from showing up by checking the "don't remind me" under preferences for overdue invoices, but that would stop ALL reminders for overdue invoices.