Issue proper invoices for purchases. (No, the paypal receipt is not an invoice. An invoice would be issued by you, the seller, and should contain the necessary information including an invoice number.)
I think for a free 'task' program this is too much.
If you want invoices and such please purchase a ERP.
No upvote from me.
Yeah, I agree it's a bit too much to integrate this into a task management system. Don't want Todoist to get too complicated.
It seems I should have created a more accurate description. I'm talking about Todoist issuing invoices to their customers (us!) for purchasing the premium service from them. Not enabling users to issue invoices to their clients.