In QBO, you can send batch reminders to customers by email on overdue invoices from the Sales Transactions page. They will receive reminder notice on each overdue invoice. It will show email sent status under 'Last Delivered' column. You still need to do this manually, sending this reminder notice automatically is not an option in QBO at this time.
Here is how:
From the left Sales dashboard > All Sales > Sales Transactions page > Click "Overdue" Money bar > Select All (next to Date column) or select invoices you want > Under Batch actions drop-down, select Send Reminders.