How can I ascertain whether a company or its shareholders deal with usurious banks?

Company managements must avoid prohibited transactions such as usury (riba), for it is one of the grave sins. It is not permissible for a shareholder to buy shares in companies that deal with usury or to act as an intermediary for them, lest he be a consumer of usury or an assistant in it. A shareholder can identify a company's involvement in usury through its prospectus and financial statements, which show loans and bank deposits, and usurious interest under the headings "financing expenses" or "other revenues," or investments in government bonds. If the company is small and does not publish financial statements, the shareholder must investigate the trustworthiness, honesty, and religiosity of those in charge of it, and seek assistance from reliable individuals who are knowledgeable about its affairs.