FINRA prohibits the payment of referral fees or splitting of commissions with individuals who are not registered with a broker-dealer. However, taking a friend out to dinner as a gesture of gratitude is allowed, as it does not involve cash or monetary compensation directly tied to the referral.

C is correct because non-monetary expressions of gratitude (like a dinner) are permitted under FINRA rules.

A is incorrect because commission splitting with unregistered individuals is prohibited.

B is incorrect because paying referral fees is also prohibited without registration.

D is incorrect because giving prepaid credit cards tied to commission income violates compensation rules.