Are we able to add one more billable user if we are at the maximum of 5 billable users already?

Hello, @skcpa124. 

I'm here to give you information about Billable Users in QuickBooks Online.

At this time, there's not an option to add-on Billable Users to a subscription plan. You can either upgrade your plan or edit your users to where you have Billable and Non-Billable. No worries, I'm going to walk you through the process of upgrading your subscription and how you can edit your Users.

Here's how you can upgrade your subscription plan:

1. Go to the Gear ⚙ icon, then Account and Settings.
2. Navigate to the Billing & Subscription tab.
3. In the QuickBooks Online section, select Upgrade. If you don't see it, you’re already using the plan with the most features.
4. Choose the plan you want, and press Upgrade.
5. Confirm your payment information and hit Save.

Here's how you can edit your Users:

1. Go to the Gear ⚙ icon, then Manage Users. If you can’t select this, you don’t have permission to manage other users. Contact an admin user for help.
2. Find the user you want to edit and press Edit in the Action column.
3. In the window that appears, choose the User type drop-down ▼ menu. Select the user type you want them to be. More options will appear on the screen depending on the user type you select. There's no limit on Non-Billable Users.
4. When you’re finished, hit Save. Ask the user to sign out and then sign in to see the change.

Let me know if there's anything else I can do for you! I'm always here to lend a helping hand.