When you delete an invoice, you delete a posted transaction, so this will affect your report totals and the customer’s balance.
Also, any unbilled, non-posted transactions that were included on the invoice become available again to be included on the next invoice you create.
To delete an invoice
Find/locate the Invoice to delete.
From the footer, click “More”.
Select Delete from the drop-down selector.
Click “Yes” to confirm.
After you delete an invoice, the only record of the invoice is in the audit log.
How to copy an Invoice in new QuickBooks Online?
Find/locate the Invoice to “Copy”.
From the footer, click “More”.
Select “Copy” from the drop-down selector.
It will crate a copy of an Invoice form.
Revise as needed and save the Invoice.
The same process also applies to Sales Receipt.