How do I add several email addresses to one customer?

Hi there. 

I'll give you options on how you can send out an invoice to multiple email addresses from one customer in QuickBooks Online (QBO) and manage your sales and income transactions accordingly. 

Before doing so, please note that there's a 100-character limit in the recipient's email address field including spaces. The system also won't allow you to send an email to the same address twice. If there's a duplicate, then that address will not receive the email. 

You can either add an email to the customer's profile or manually type in their email addresses in the Cc (carbon copy) and Bcc (blind carbon copy) sections before sending forms. We just need to separate each email with a comma.

Option 1. To add an email to the customer's profile, follow these steps:
 

1. Go to the Sales menu, then choose Customers.
2. Choose a customer.
3. Select the Customer Details tab, then click Edit.
4. You can enter multiple email addresses in the Email field by separating each with a comma.
5. Save once done.

Option 2. To manually type in email addresses in the Cc and Bcc sections:
 

1. Go to the Sales menu, then select Invoices.
2. Choose an invoice then click on Edit.
3. From the invoice page, click on the Cc/Bcc hyperlink.
   
   
    

Moreover, there are times when email fails to deliver or the customer doesn't receive any. To fix this, here's an article that highlights the steps to ensure that your customer receives their invoices and pay you on time: Fix undelivered invoices in QuickBooks Online.

If you have other concerns about managing customers and invoices in QBO, please don't hesitate to let me know in the comments below. I'll gladly help. Take care, and I wish you continued success.