Kickback schemes generally involve:

Kickback schemes typically entail situations where an employee receives a portion of the profits or payments resulting from inflated invoices. This often occurs when a supplier or vendor charges a company more than necessary, and the employee receives a kickback as a reward for choosing that vendor. This creates a conflict of interest because the employee benefits financially from transactions that may not serve the company's best interests.

When examining the other options, direct payments to customers do not characterize kickback schemes, as these payments do not involve an exchange benefiting employees at the company's expense. Legal actions from vendors against employees are not typical of kickback schemes, as such actions generally arise from contractual disputes rather than illicit activities. Lastly, payment for services completed can be legitimate when transactions are fair and transparent, contrasting sharply with the deceptive nature of kickbacks, which depend on dishonesty for profit. Thus, the option regarding employees receiving a share of inflated invoices accurately reflects the essence of kickback schemes.