there is a big difference between a "kickback" and a referral fee.
The difference lies in who the recipient is.
If it is the recipient's job to procure the services and he requires financial or other gain to award the contract, that is a kickback.
If the recipient is the owner of the property, or he has no duty to procure the services either contracts with you for a predetermined discount or refers you to another decisionmaker in exchange for a referral fee, that is a simple referral.
I've given free filter service to business owners as a thanks for their commercial account. Most of them refuse the offer because they want to avoid anything that looks like a kickback. Others who understand the difference will sometimes take me up on the offer.
Am i wrong here? This was what i learned in college so it probably is wrong! :d
i offer a referral fee to all my customers.