The ability to un-void an invoice is currently unavailable in QuickBooks Online (QBO), @customer12_2.
The most common and efficient approach in QBO for handling a voided invoice is to recreate it. To expedite the process, you can utilize the Copy feature or refer to the Audit Log to access the original details and re-enter the transaction.
Here’s how to copy the invoice:
Go to the list of your invoices and open the one that is marked as Voided.
Find the More actions button at the bottom.
Select Make a Copy.
Please note that attachments remain in the Attachments section even if the transaction is deleted, so you can re-link them to the new invoice.