Hi there, cafsinc.

The attachments will not automatically send to the customer. You'll have the option to uncheck the attachment to email box so it will not include this when emailing the invoice.

Here's how:

1. Click the Plus icon at the left panel and select Invoice.

2. From the Customer drop down arrow, select a customer. Make sure all of their info is correct, especially their email address.

3. On the Invoice page, click Attachments.

4. Browse the file you want to add, then click Open to add.

5. Make sure to remove the checkmark in the Attach to email box.

6. Fill in the other necessary fields.

7. Click the Save and send button.

I attached screenshot below for visual reference.

Please check this article what are transactions can keep attachments: Attachments in QuickBooks Online.

Please know that you're always welcome to post if you have any other concerns. Wishing you and your business continued success.