We have many clients, usually we send an invoice every 30 days per client). Is there a feature to remind us when to *send* an invoice? (Not when it's due)?

It's nice to have you in the Community, @useradam4. I’m here to make sure that you'll be able to send an invoice reminder in QuickBooks Online. 

You have the option of creating a recurring template for recurring transactions. This way, you’ll be able to set reminders for your invoices. Here's how:

1. Go to the Gear icon at the top, then select Recurring Transactions.
2. Click on the New button in the upper right hand.
3. In the Select Transaction Type window, select Invoice.
4. Click on OK.
5. On the Recurring Invoice page, choose a Type: Scheduled, unscheduled or reminder.
6. Fill in the necessary fields.
7. Choose Save template when done.
   
   

For more in-depth information about creating recurring invoices, check out these articles: 

• Set Up a Recurring Invoice for Customers
• Create templates for recurring transactions

If you need to make some changes to your recurring templates, see this article for the steps: Edit a recurring template.

Please let me know if you have additional questions or concerns about managing your invoices. You can reach out to the Community at any time. Take care!