How do I add late fees onto unpaid invoices?

I'm here to help you add a late fee to an unpaid invoice, @tworivershomesol.

You can set up a late fee in QuickBooks Online (QBO) and the program will automatically calculate and apply it to overdue invoices. Here's how:

1. Go to the Gear icon and select Account and settings to turn on the late fee settings. 
2. Navigate to the Sales menu, and in the Late fees section, select Edit.
3. Turn on the Default charge applied to overdue invoices switch.
4. Enter the Amount and/or Percent (%) of the fee and select how often you charge customers in the Frequency dropdown.
5. When done, select Save.

However, late fees won't show up if the invoices are:

• was already overdue before turning on the default late fee settings
• exceeds up to six months overdue
• invoice is still unpaid but in a closed period

If that's the case, you have to manually add the late fee to the invoice as a line item. Just edit to add the Late fee item and enter the amount (this will show once you turn on the Late fee settings).

For reference, check out this guide: Apply late fees to overdue invoices automatically in QuickBooks Online.

Furthermore, here's a helpful guide that you can read when it's time to record your customer's payments: Record invoice payments in QuickBooks Online.

If you have any other queries about handling late fees to unpaid invoices, please don't hesitate to leave a reply below. I'm just a post away to help. Have a good day ahead.