Thanks for coming back for more support, @ChelleMtoo. Let me chime in and add more insights about what you're trying to achieve today. 

As mentioned by my peer @Mark_R, QuickBooks only supports assigning classes to Accounts Payable (A/P) by creating a check or an expense transaction. This is why you're unable to assign the bill payment to a class. 

Moreover, QuickBooks doesn't have a specific Balance Sheet report that's showing by class.

Should you need to assign classes to your Accounts Payable (A/P) transactions instead, you may follow the steps he outlined above. 

For future reference, read through these articles:

• Track your transactions by class. It helps you learn about tagging a class to a transaction. 
• Run reports by class. it helps you learn about how to view your profitability and spending by class. 

Feel free to message again if you have additional questions. We're always delighted to help.