When you void an uncashed check from a prior year, there is supposed to be a way that Quickbooks will ask if you want it to create the two ledger entries.

dlynx@kirklandar 

It would be great if there was and it's been requested a lot but QBO isn't that smart.  You have to reverse it manually.  Create a deposit in the current period to offset the check you want to void.  Then, re-issue a new check.  Use a Clearing Account as the offset or whatever account you like.  The next time you reconcile, clear the check you want to void against the deposit.  Some people like to issue a new check, then void it, and change the old check number to the new check number.  I don't like that method because you end up with a missing check number.  

dlynx@kirklandar  RE: When you void an uncashed check from a prior year, there is supposed to be a way that Quickbooks will ask if you want it to create the two ledger entries.

You're thinking of real QuickBooks, the Desktop version.   QuickBooks Online can't be expected to have such useful features. They're struggling just to keep the system up - most of the time.