Hello root7,

Thanks for posting your question in the Community. I'm here to provide information about setting up alerts on past due invoices.

In QuickBooks Online, you can send invoices through email for invoices that are past due. Since reminders don't send automatically, you still need to send them manually.

To set up Invoice Reminders, you follow the outlined steps in this article:

How to set up invoice reminders.

Once done, you can now send reminders in the system by following these steps:

1. On the left navigation bar, click Sales.
2. Go to the All Sales tab.
3. Put a check mark beside the invoice you want to send.
4. Click the drop-down arrow next to Batch actions.
5. Click Send reminders.

Please don't hesitate to reach out if you need any help concerning QuickBooks Online. The Community is always around for you.