What is the best way to get a QB notice that it is time to contact a customer

Hi, @HR49. I can share a QuickBooks Online (QBO) feature that allows this kind of notification.

You'll have to create a recurring transaction to get a notice from QBO that it is time to contact customers. Recurring transactions allow automation of transactions like invoices and bill payments. This feature also includes an automated schedule to remind you to create the transactions.

Since you have 300 customers, you will need to create individual recurring invoice transactions for each of them. Let me show you how to create one for a customer.

1. Go to the Gear icon and select Recurring transactions.
2. Select New.
3. Choose "Invoice" from the Transaction Type dropdown.
4. In your recurring invoice sheet, select Reminder and determine the days before the transaction date.
5. Select Yearly from the Interval dropdown and determine the specific dates.
6. Enter other necessary fields in your template.
7. Select Save template.

Please see the image below for reference:

Also, I'm adding this article on how to view all your recurring transactions in one place and see which accounts they're linked to on your chart of accounts: Review your recurring transactions in QuickBooks Online. 

You're always welcome in the Community should you have further questions about creating reminders in QBO. Stay safe.