Thanks for joining this thread, @CFuqua.
The option to add classes to prior payrolls is unavailable in QuickBooks Online. You can only assign classes for payroll moving forward. This is because changing already created paychecks may affect future ones.
Here's an article that will give you more info about prior payroll: Set up a prior payroll for QuickBooks Online Payroll.
Also, you may visit these helpful articles to guide and give more details about managing classes in QuickBooks Online:
Please know that you're always welcome to post again if you have any other payroll concerns. I'm always here to help. Wishing you and your business continued success.
