Am I able to recover a deleted invoice?

Hi @timjw 

Retrieving the deleted invoice in QuickBooks Self-Employed (QBSE) is presently unavailable. With this, I'd suggest re-creating manually  in your account. If you've sent the invoice before to your customers, you might want to ask them for a copy for your reference. 

Once you have done creating the invoice, you have an option to copy, export as pdf, and send the transaction to your own email for your back up. 

See the screenshot below for your reference:

You can also visit this link for further assistance QuickBooks Self Employed 

Hope these steps can help, as I understand how important having your record is to the success and transparency of your business.