How do I add more than one contact to a customer

Hello, @ShaneSpuds10.

If you want to record multiple contacts on your customer's information, then it isn't possible as of the moment. You may create a sub-customer to have a difference contact.

Here's how:

1. Select Sales on the left menu and go to the Customers tab.
2. Click the New customer button.
3. Enter the needed information in the Customer information window.
4. Mark the Is sub-customer box and enter the parent customer, then select whether you'll bill with this customer or with the parent.
5. Click Save.

On the other hand, if you're trying to add multiple contacts when sending transactions in QuickBooks Online, you can add multiple contact details (email) using commas. 

Let me know if you have any other questions. I'm always here to help. Have a good day!