Hi there, Dpettit1.
I can share some insights about how classes work in QuickBooks Online.
The class that you've added to your employees will only affect the current and future payroll taxes. The previous year's payroll taxes won't be allocated to the class that you've just assigned to your employees.
You may need to delete and then recreate your past payrolls so that the class will be added. Before diving in, please take note that you can only create unscheduled checks for the current pay period all the way back to pay periods dating 6 months ago. Here's how to do it:
For the payrolls from the past 7 months and above, you'll want to consider exporting your payroll reports to an Excel file and then add the class from there.
Additionally, I encourage reading this article to help better manage your classes in QuickBooks Online.
You can always find me here if you have any other concerns or follow-up questions about classes. Assistance is just a comment away.