I do NOT have "Track expenses & items by customer" available to me as an option under "Account & Settings" then "Expenses". Why not?

I can see that you're trying to activate the Billable Expense feature, jfsmith6163-gma.

The Messages option is also used for Purchase Orders. Please know that both of these feature are offered in QuickBooks Online Plus and Advanced versions.

It's possible that you're using either Essentials or Simple Start. This can be the reason why you're unable to see these options under the Accounts and Settings.

You'll want to upgrade your account to be able to activate and use these features. Here's how: 

1. Go back to the Gear icon and select  Account and settings.
2. Proceed to the Billing & Subscription tab.
3. Click Upgrade your plan under the QuickBooks Online section, 
4. Select Plus or Advanced, then click Choose plan.
5. Follow the on-screen steps to upgrade your plan.

Once done, follow these steps on how to activate the features that you need for your business:

• Enter Billable Expenses
• Enter Billable Time by Job in QuickBooks Online
• Create and Send Purchase Orders in QuickBooks Online

Post more questions or reply to me if you have follow-up questions about the information I've shared with you. We're always here to offer our help anytime you need it.