Thanks for reaching out to us, MarketingBiz12.

You can use the Audit log report to determine which customers received invoice reminders. This section contains a record of all activity in your QuickBooks Online account. I'll show you how.

1. Go to the Gear icon
2. Under the Tools column, select Audit Log.
3. Click the Filter button.
4. Use the fields on the Filter panel to choose the appropriate User, Date, or Events filter to narrow the results.
5. Hit Apply.

Please include your email address in the Carbon Copy (CC) section. It guarantees you receive a copy of every invoice sent through QuickBooks Online.

Here's how:

1. Go to the Gear icon, then select Account and Settings.
2. From the left menu, click Sales.
3. In the Messages section, you can enter your email address under Copy (Cc) new invoices to address.
4. Click Save and then Done.

Refer to this article for more details: Email a sales form or report to multiple email addresses.

You can also read this resource to learn how to automate sending invoice reminders: Send invoice reminders automatically or manually in QuickBooks Online.

After receiving payment for the invoices you sent, see the following article for instructions on recording this transaction: Record invoice payments in QuickBooks Online.

If you have any further questions, please leave them in the comments section. I'm always available to assist here in the Community.