I would like to be reminded if the invoice is repeating so I can avoid double invoicing?

I'll share how it works in QuickBooks Online, Dyana-nb.

You're unable to set up a reminder for a duplicate invoice. You'll want to pull up the Invoice List report to check the transactions you've created for the customer. It'll help you know if there's a duplicate invoice. Here's how:

1. Click Reports.
2. Enter Invoice List in the Find report by name field.
3. Click Customize.
4. Go to Filter.
5. Click the Customer drop-down, then select the specific customer.
6. Click Run report. 

I'll share the reference on how to customise the report. It'll help you focus on the details that matter most to you.

If there's anything else that you need, you can always get back to this thread. Keep safe!