Hello there, susan13.

I'm here to help answer any question you may have with QuickBooks Online Mobile.

If you're on the process of creating the expense, you'll have the option to enable the Billable option through the mobile app.

I'm adding a screenshot below for your reference:

You can also follow these steps to edit an expense transaction to make it billable:

1. Go to Vendors.
2. Select the vendor.
3. Go to the Activities tab.
4. Select to open the expense transaction.
5. Click the pencil icon (see screenshot below).
6. Change to Billable expense.
7. Click Done.

Thanks for coming to the Community, I'll keep an eye out for your response.