I have mistakenly voided an invoice which has been paid, how do i unvoid???

Hi bluebushgardenin, 

For a voided invoice, you may need to recreate or edit it in QuickBooks Online. If you void an invoice, QuickBooks does not void any payment that you’ve recorded for the invoice.

Here's how you can use the Audit log to see the details previously entered on a voided invoice. 

1. Go to Gear icon and select Audit log. 
2. Click on Filter.
3. Use the fields on the Filter panel to choose the appropriate User, Date, or Events filter to narrow the results.
4. Tick Transactions.
5. On Show drop-down menu, select Deleted/Voided Transactions.
6. Select Apply. 

Then, recreate or edit the voided invoice which can be found on your customer's transaction list. 

Please reach out again if you have any other questions. Have a great day!