Agregar Funcionalidad a SMS (School Management System) PHP Laravel

The (Original) software is Oraschool. I need to add the functionality of using automatic discount for past due installments (apply discount to a rate until the expiration date has passed). Because right now the discount module only applies statically (for one time, and manually). It would be useful to be able to apply it through the group of rates, that is, create a discount and assign it to all the rates that are part of that group. It should be noted that someone already worked on trying to add this and could not. I leave some code in the system.