Here is how to send customers clients batch reminders by email on past due invoices in QuickBooks Online:
From the left dashboard > Click Sales tab > Select All Sales > Click Unpaid Last 365 Days (Overdue) Money Bar > Optional: Go to middle Gear at the far right, click “Show more” link and add “Email” column. This is to ensure you’ve email address for customers. > Select “Select All” checkbox (left of Batch actions) > Choose Batch actions drop-down and select “batch Reminders” > Done. It will send customers batch reminders by email.

Currently, there is no option to send reminders automatically when the invoices are due.

Here is our video tutorial:

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