Travel and entertainment expenses have long been a haven for abuse, but since the dollar amounts are often insubstantial, companies don't always pay close attention to them. Companies are now finding, though, that they can be a conduit for bribes. "If T&E goes unchecked, it can make a company susceptible to allegations of corruption," says Andrew Levi, head of the Miami office at investigation firm Nardello & Co. How to root out fraud? More inside.