Where do I find a specific invoice, and how do I know if it's overdue?

Go to Billing invoices. Invoices are grouped into tabs — All, Pending, Overdue, Paid, Credit notes, Statements — each with a count. Use search or 'Filters' to narrow it down, or check the box to 'Export invoices' in bulk.

Billing invoices — status tabs and the full invoice list.