How do you send an overdue invoice reminder on a mobile device

Welcome to the Community, @jethrohenderson1.

Currently, the ability to send an overdue invoice reminder in QuickBooks Online (QBO) Mobile app is unavailable. This can only be done by logging into your account using a web browser.

Before doing so, ensure to set up an invoice reminder in the Account and Settings. Here's how:

1. In QBO, go to the Gear icon at the top right to get to the Account and Settings. 
2. Choose the Sales menu at the left pane, then click the Edit (pencil) icon in the Reminders section. 
3. Update the Subject and Email message.
4. Hit Save and Done to complete.

After that, here are the steps on how to manually send a reminder to all overdue invoices:

1. Go the Sales menu at the left pane to get to the Invoices page.
2. On the overdue invoice, click the drop-down option under the Action column.
3. Choose Send reminder, then hit Send. 

In addition, QBO also have the ability to automatically send an invoice reminder. For more information about this feature, check out this article: Automate invoice reminders in QuickBooks Online.

Please leave a comment below if you have any other concerns or questions, and I'll get back to you right away. I'm always here to help. Have a great day!