I'll help with your question about invoice's due dates, vitos1032.
We're unable to set permanent due dates in QuickBooks Self-Employed. For now, you'll need to manually select the date when creating an invoice.
Also, please take note that the invoicing feature in the program is to create the transaction so you can send it to your customers and collect the payments as well. Here are a few of our quick guides for more details:
As always, you can always reach out to us again if you have other questions.