Hello everyone! This is a really annoying issue, and QuickBooks needs to warn users that they are selecting the wrong payroll account for accounting purposes (example - they know that I am using a bank for payroll, so why not warn that I was using the Cash account?)

Here is the solution that worked for me:

1. In the Chart of Accounts, go to the account that the paychecks were wrongly posted to. In my scenario I posted to the Cash account instead of my checking account.

2. Create a new journal entry Debiting the wrong account and Crediting the correct account for each amount wrongly posted (tedious, but has to be done to clear your negative balance on the wrong account). Make sure that the journal dates match the original transaction. 

3. Navigate to Bookkeeping -> Transactions

4. The existing Transactions should be listed here. If you don't see them, click Categorize and search for the existing transactions (in my case this was IRS or Payroll). Click Undo on each of these transactions that were affected

5. This is the last step, which is on the same screen under 'For Review'. We need to match up the journal entries with the actual transactions. When categorizing the transactions that you clicked 'Undo' on, click the transaction, and then click 'Find match' and select the manual journal entry that you did.

Now your P&L will appear correct and bank accounts will look good! Yay!