A fine of $600,000 and an order of more than $648,000 in restitution and interest be paid to over 3,600 customers has been imposed on Citi.

FINRA Market Regulation executive vice president Thomas Gira said that the regulatory authority was committed to ensuring that customers who purchase and sell securities, including corporate and agency bonds, receive fair prices.

"The markups and markdowns charged by Citi International were outside of appropriate standards for fair pricing in debt transactions, and FINRA will continue to identify and address transactions that violate fair pricing standards, regardless of whether a markup or markdown is above or below 5 percent," Gira added.

FINRA has alleged that the excessive markups and markdowns charged by Citi from July 2007 through September 2010 ranged from 2.73% to over 10% given market conditions, cost of executing the transactions and value of the services rendered to the customers.

Additionally, from April 2009 through June 2009, Citi International failed to use reasonable diligence to buy or sell corporate bonds, which could have resulted in favourable prices to its customers under prevailing market conditions.

Citi International neither admitted nor denied the charges, however, FINRA has ordered Citi to revise its written supervisory procedures on supervisory review of markups and markdowns, and best execution in fixed income transactions with its customers.