You can choose to set when an invoice becomes past due and add a late fee.
To do this go to Settings (the gear icon on the top right)
Once on settings, click “Invoices & Estimates”
Toward the bottom of the screen is the section “Invoice Settings”
First, enter the number of days after the invoice is sent that you want the invoice to become past due and add a late fee to the invoice.
In this example, I chose 20 days.
Note: Percentage is only available if you have auto-charge enabled.
You can add more rules by clicking the green “+ Add Late Fee Rule” button.
Be sure to click the blue Save button when finished to save the new late fee rules.