Setting up Billing

I have a child care management app. Child Care sign up and manage their businesses on it, including scheduling and billing the parents. I’m trying to find a good way to setup the database and other background functions to bill the parents.

Database currently has a scheduling thing that will track the hours the child is scheduled and also an hourly rate thing to calculate how much to bill depending on how many hours the child are scheduled.

Example would be, Child is scheduled on Monday from 8am to 5pm. thats 9 Hours at say $5/hour for a total of $45 for the day.

What I need is how to put these ‘things’ together (scheduling and rate things) for multiple different schedules and different hourly rate scenarios.

IE - the child care starts out at $5/hour and then changes the rate at some point to $6/hour - How do I separate the schedule things to identify which schedules go to which hourly rate thing.

IE - parents are Divorced - Mother pays Week 1, Father pays week 2, etc. How to identify which parent is paying which schedules. Along with late fees should be associated to the individual parent that is late. Not to both since they are divorced

IE - Speaking of divorced parents. One may pay over the amount owed. Such as the mother only owes $100 for the week but pays $140 to have a $40 credit. That $40 credit should only be applied to the mother, and not the father when he pays.

Hope this all makes sense. hit me up with questions