Cash Back Reward Program - Is it Illegal? Don't See it

Hello Guys,

I have a question, I am looking to start a business plan, and it involves a "Cash Back" reward program, where we would literally send them a check each month based on their reward points, this is sort of in the retail industry.

Is this illegal? I am asking as I see a bunch of retail stores that have Reward Programs, but they all do like coupons, percentage off, etc but none that offer a "Cash Back" option, so trying to figure out why, is it illegal or something, or just don't want to get rid of "Cash".

Thanks in advance for any answers we get!