In the context of investment banking, product control is the department responsible for the daily monitoring of trade activity to make sure that it is within acceptable limits, according to Wikipedia. Product controllers complete all of the financial and accounting reporting for the bank's trading desk. The product controller is responsible for making sure that the trader's books reflect fair market pricing and the daily monitoring of assigned portfolios.
Robert Walters, a large recruiting firm that specializes in placing candidates in banking and finance, notes that the primary function of a product controller is to work closely with front-office traders and the valuation department to produce daily profit and loss reports for products traded. Product traders are responsible for looking for and analyzing abnormalities in trading. This position assists the bank in determining and forecasting market trends, analyzing risk and monitoring product performance. Product controllers also assist the bank in assessing trader performance in correlation with the market.
Robert Walters also explains that controllers provide bank traders with product information and valuable stock market information to assist in increasing profits and lowering the bank's potential financial risk. People in this position often work closely with the main staff of the bank along with traders and bank operations staff. Product controllers may report to, or take direction from, a central product control department.