However, to this question , once deleted - invoices can not be reinstated. There is no wayback machine that will recover anything deleted. There is not even a "revert" button as in desktop versions that allow reversion to original during an edit but prior to saving.
Audit log can help you see what might have been in something deleted but no method exists outside of having used a third party tool prior to deletion
I have deleted a invoice, then I want to use the old invoice no. How to do ?
My bad. I accuse you of responding to a different thread and it was I that did so. I thought it was about resurrecting a deleted invoice - hence my instructions that had nothing to do with it. Blame it on working from home, lol