If the U.S. government or another private party has already filed a FCA lawsuit based on the same fraud allegations as your lawsuit, the law bars you from bringing your lawsuit. Your suit cannot be based upon publicly available information. But if your allegations are different from those of the earlier suit, the first to file rule may not apply. Unfortunately, you and your attorney may have no way of knowing in advance of filing whether a lawsuit has already been filed, because cases must be filed under seal.