FINRA (Financial Industry Regulatory Authority) Is The Largest Self-regulatory Organization In The US That Distributes Licenses And Regulates Daily Trading To More Than 4,500 Brokerage Firms. The Agency Is The Gateway Through Which All Securities Firms Must Pass In Order To Do Business In The US. FINRA Implements Regulations To Protect Investors And Ensure Markets Function Fairly, Such As Enforcing Compliance With Marketing And Margin Rules, Day-to-day Trader Requirements And Others. FINRA Is Also Responsible For Membership Registration, Certification And Arbitration.