How do I show the project on the invoice so the customers know what the project is that I am billing for?

Welcome and thanks for reaching out to the Community, @userbrandonjamesfloo.

In QuickBooks Online (QBO), the option to show a project on the invoice is currently unavailable. As a workaround, you can customize the invoice template that you're using to add a custom field.

Here's how:

1. In QBO, go to the Gear icon at the top right to get to the Custom Form Styles.
2. Locate the template, then tick Edit under the Action column.
3. Proceed to the Content tab, and click the Edit (pencil) icon in the header part of the template.
4. Select +Custom field to add extra fields. 
5. Hit Done to complete.

Once you create an invoice, you can use the custom field to manually enter the project.

While this option isn't available yet, I recommend visiting our Blog site. This is where we share recent happenings and future developments, such as updates to newly added features.

To learn more about managing projects in QBO, I suggest checking out this article: Set up and create projects in QuickBooks Online.

Feel free to comment below if you have any other questions or concerns. I'm more than willing to help. Have a wonderful day!

Come on QuickBooks!

This is truly ridiculous, why don't you have a PROJECT field available as an EZ Map field option?!, e.g.

<project>

Which Project an invoice relates to is absolutely fundamental to any invoice sent to the Customer.

Please sort this urgently.