Add late fee to authorize.net payment tool

Please list simple steps to add a late fee after a deadline has passed in one of two ways: in the original form prior to form going live or after the deadline has passed.

Please help.  I need simple steps associated with the current jotform format.

The easiest way to set up a late fee without having to completely change the way your form is set up would be to simply add a product after your deadline.  Label this product as "Late Fee" then set it to be selected by default and required:

You could do this automatically with a date field and conditions, but it would require setting up all your products outside the payment field, using calculations and various other modifications.

Thank you, that is exactly what I needed to know!

Very welcome!  If there is anything else we can help with, just let us know.