Good day, @RyanC3PO.

Let me share with you some insights about the Chart of Accounts in QuickBooks Online. 

Before we proceed, can you verify with me if you're referring to the Billable Expense Income account in QuickBooks?  

If so, this account is one of the default accounts in the program. This is categorized as Income in Account Type and Sales of Product Income in Detail Type. 

If you're trying to create a new account for Billable Expenses, then you can freely select its account type and detail type. To ensure everything is properly set up, reach out to your accountant for further guidance. 

In case you're referring to categorizing Billable Expenses as income and expense, then this option isn't available. You can't use both of these categories as an account type.

You can use an Income account for transactions and payments you get from your normal day-to-day business, such as sales revenue or income for services rendered. On the other hand, use the Expenses account to track transactions of money you spend on expenses related to normal business operations. Examples are advertising and promotion, office supplies, and rent.

For more details, you can refer to this article: What the chart of accounts is and why it’s important to set up correctly in QuickBooks Online.

To find out how to use account types and detail types in your chart of accounts, you can check it out here: Learn about account types and detail types in QBO.

If you're referring to something else, feel free to add them on this thread. I'll be more than happy to help you out, @RyanC3PO. Have a good one.