Adding a second email to an existing client project is a great idea, Sadie. However, this feature isn't available at the moment.
In the meantime, I recommend sending feedback to our product development team. They can consider your suggestions for future updates to add a second email for existing client projects in QuickBooks Online (QBO). Here’s how:
- Click on the Gear icon, then choose Feedback.
- Share your product improvement ideas.
- Click Next to submit.

You can keep track of your ideas or recommendations by visiting the QBO Feature Requests website.
Also, you might want to generate the Project Profitability report to track your income and cost transactions. Here's how:
- Navigate to Projects in the left navigation panel.
- Select the specific projects for which you want to analyze income and costs.
- Click on Project Reports and then view the Project Profitability.
Feel free to click Reply if you have any other concerns about projects.