Good day, @sandra18.

Thank you for posting in the Community, it's my pleasure to provide you the information where you can retrieve a deleted invoice.

Restoring a deleted transaction in QuickBooks Online is currently unavailable.  However, you can check the Audit Log to look at the information and re-create the deleted transaction.

Here's how:

1. Go to the Gear icon then select Audit Log.
2. Click the drop-down arrow beside Filter.
3. Select All Users and All dates.
4. Under Events, tick the radio button beside the Show only these events option.
5. Check the box beside Transactions and click the Apply button.
6. Look for the invoice, and click View under History column.
7. Then, re-create the invoice from the Plus sign (+) at the top.
8. Select Invoice.
9. Enter the needed information, and click Save.

I also got an article for more information on how to: Restore deleted transactions. Once you've done recreate the invoice, please check this article for further guidance: How to create an invoice.

Please feel free to read these helpful articles for future reference:

• Send an invoice.
• Customise your invoices, quotes and sales receipts in QuickBooks Online.

Please keep me posted how it goes or if you need additional assistance. I'll be happy to help. All the best!