Hello blalock325.
I'm here to provide some additional clarification on your question regarding the limit for eCheck payments in QuickBooks Online.
Our Merchant Services Team may provide processing limits and assign a maximum dollar amount per transaction for using the services. However, you have the option to request a limit increase on the per-transaction payments.
For additional insight into QuickBooks Payments, such as processing limits, I'm adding an article for you: Intuit Payments Merchant Agreement.
I also encourage you to reach out to our Merchant Services Team (scroll down to QuickBooks Payments support) to know more about the process.
Please don't hesitate to post any questions you may have below. I'll be here to help.