Hello patrick-kennedy,
You can create a reminder in your QuickBooks version. However, it isn't possible to send it every week to customers who have 90 days or more worth of overdue.
Let me walk you through how.
- Click Gear, then click Recurring Transactions.
- Click New. Then, select a Transaction Type.
- Click OK.
- In the Recurring [transaction] page, enter the Interval, Start date, End, and other information.
- Click Save template.
Please refer to this article for details: Schedule recurring transactions created with a template.
Here's an article for future help: Run Accounts Receivable Aging Summary report.
If you have additional questions, please don't hesitate to reach out anytime.