I can't add an invoice without putting in a customers email address. How can I remove this requirement?

Hello there, dadsboy251163.

Let me provide some information on how sales transactions like invoice work in QuickBooks Online.

When we create an invoice, it can be saved without the email address of our customer. We will only need to make sure that the Save and Send button is not clicked. Otherwise, it'll ask you to enter their email address. With that being said, there are options that you can click aside from saving and sending this transaction.

For visual reference, you can take a look at the screenshot below:

• Click the Save button instead of the Save and Send one.
• Click the Save and Send drop-down arrow. Then, select either Save and New or Save and Close.

In recording the invoice payment, we can use this link as a reference on how to do it within QuickBooks Online. Also, you can visit this article from time to time to get more details about sales transactions like how to view and manage them.

If you have other questions about transactions in QBO, please tap me on my shoulder. I'd love to assist you more. Stay safe, and be well!