Hi Amy,

• If the transaction is from a closed year, there's no way to delete or modify it.
• You can apply transactions to it (Receipts, Payments, Credit Memos, etc) in your current open periods, which will remove them from reports run after the date of the new transaction.  Refer to the articles listed in the Related Resources section for more information on creating and applying these transactions.
• The items will continue to show up on the reports when run for the dates between the original transaction and the new one.

If those invoices were previously 'written off' through a journal entry my guess is your AP Aging doesn't match your Balance Sheet.  In which case, you could adjust the invoices against AP using the Payments screen, check off the invoices and then go to the Apply to Expenses tab and offset the amounts as a negative and choose the AP account.  Only do this if your AP doesn't match your Balance Sheet AP balance.  Otherwise, if they were old bills that don't need to be paid or were paid through a CC and that was entered as an expense you would want to write them off using the same steps but choose the related expense account to reverse out prior years duplicate expenses in the current year.  There is no other way to just delete them because there are other impacts to doing that.  

I discovered a solution on the receivables side --

I accidentally imported a sales invoice with a date in a closed period. To correct, I simply imported a reversal of the original invoice, with the same incorrect date. 

Then I was able to 'receive money'  on both of the invoices by selected both outstanding invoices, cash was unaffected.

I then imported the correct date on a new invoice and my AR balance is correct, and neither of the invoices in the closed period show as outstanding.