I have answer to your late fees question, @HeatherMarie1. 

I'll share some information on how the late fees apply to the past due invoices in QuickBooks Online. This way, I can guide you accordingly in managing your sales transactions. 

QuickBooks only calculates and applies late fees to overdue invoices the day after you turn on the late fee setting. For example, you turned on late fees on 05/10/2023. Then only those past due on 5/10/2023 and moving forward will have late fees (depending on the grace period you set). This means that any existing past-due invoices won't have late fees enabled for them.

You can tell if an invoice is eligible when you open it. In the header, under the due date, you'll see this:

For invoices created after late fees in QuickBooks Online were enabled, you'll see this:

Once you enable late fees, when you do encounter a customer with a past due invoice, you'll see that invoice automatically updated with late fees added as a line item.

But no worries, you can still manually apply late fees as a line item on older invoices. You can refer to the steps I've outlined above. 

In addition, if you want to check your late fee amount, you can go to your Chart of Accounts and search Late Fee Income. Refer to the sample screenshot below: 

Moreover, check out the following articles below to learn how to edit the default late fee settings and send invoice reminders in QuickBooks:

• Apply late fees to overdue invoices automatically in QuickBooks Online.
• Send invoice reminders automatically or manually in QuickBooks Online. 

You can reply directly in this thread if you have additional questions about late fees in QuickBooks. I'd be willing to lend you a hand. Keep safe.