Hi LV Mrf,
Welcome to the Community. It's important to enter your customer information correctly to keep your account up to date. QuickBooks Online is a great program that gives you the ability to easily track your sales and expenses. I'd be glad to help.
If you'd like to change the customer's email, I encourage you to follow these steps.
- Click on Sales on the left navigation menu.
- Select Customer.
- Click on the customer of your choice.
- Select Edit and change the customer email.
- Click on Save.
Let me know if you have questions, I'll be happy to help.