It's so important to be able to differentiate the projects in your invoice for your customer. And I can help, @roberta-tpclawye.

To create a single invoice for multiple projects for the same customer, all you need to do is select the customer's name on the transaction page. Doing this will show all the billable expenses for that particular customer.

1. Select + New.
2. Then select Invoice.
3. From the Customer ▼ dropdown, select the customer's name. 
4. Review the Invoice date. If you need to, change the due date in the Terms ▼ dropdown.
5. In the Add to Invoice section, select all the billable expenses by clicking Add. You can also click Add all to select them all at once.
6. When you're ready, click Save and close.

That's it! Now you can include multiple projects on your one invoice. Here's a really great article for you to look at as well: Create invoices in QuickBooks Online.

I'm here for all your invoicing questions! Let me know if I can help with anything else by leaving a comment below.