Thanks for coming back and clarifying what QuickBooks version you're using, Skyline.
In QuickBooks Desktop, your customers can pay for their invoices online with a credit card, debit card, and ACH bank transfer. However, the option to save their ACH info when processing the payment is unavailable. We can only save the credit card information in the Payment Settings section of the customer profile. Wherein you can process payments right in QuickBooks by turning on online payments for the invoices you an email to customers. Customers can pay their invoices by credit card or ACH bank transfer by following the link in the email to pay. To learn more about this one, see Receive and process payments in QuickBooks Desktop article.
Also, if you are processing e-checks in QuickBooks, you'll have to manually enter the ACH information of your customer. From there, you can enter the Account number and Routing number on the check. and select the Customer authorization section on how your customer authorized the check. For the steps and details, see the Process e-checks or scan check payments in QuickBooks Desktop article.
Feel free to visit our QuickBooks Payments page for more insights about managing and processing your payments.
I'll be right here to continue helping if you have any other concerns or questions about QuickBooks. Assistance is just a post away. Take care always.