In the past few years, the U.S. has put in place some of the most stringent immigration related measures ever. Although you or your employees may have crossed the U.S. border several times without a problem or without being told you need a visa, it does not mean that you will not encounter problems in the future.
Not only is there the risk of being held for several hours while U.S. immigration officials question and investigate any traveler, such incidents could have long-term ramifications, even years down the line and even if you or your employee are no longer with your company.
As part of ongoing investigations, the US Immigration and Customs Enforcement (ICE) are scrutinizing companies to ensure employees are working under the correct status in the US. Violations may result in serious consequences for both the companies and the relevant employees. To minimize these risks, you may want to consider obtaining the proper visa/s.