Ok, I'm adding my 2 infuriated cents here as well.  I've been a CPA for more than 30yrs and worked in multi-billion dollar companies.  So having CS responding with canned responses like "here's how to create a journal entry" or "contact your accountant" is pathetic.  I've been trying all kinds of workarounds.   The void should be a NEW transaction that re-instates the payable but doesn't change the original payment transaction (and therefore doesn't retroactively change my books/bank recs from 3 months ago, or the prior tax year!!!).  Then I should be able to match up the refunded payment with the new transaction created by the Void.  Not complex.  I've used dozens of accounting software packages, and they all would show a Payment as one transaction, and a Void as another, so you preserve the history of what actually happened WHEN it happened.  Accounting Software 101. 

While Bill.com might void the payment itself (totally fine), the issue is with how QBO is recognizing that void in their own software.  Passing the buck to Bill.com is B.S.  Insane.  ESPECIALLY since they market the "QBO Online Bill Pay" as a QBO feature.