I know others who have accidentally paid a bill twice, or simply overpaid a bill because they didn't have the exact amount of the bill handy and wasn't able to look up the specifics. In most cases, the companies in question would just credit the difference. However, it turns out that Citibank had a different idea. It apparently decided that if you overpaid a bill, you really were just donating free money to Citibank executives' bonus fund. The company actually had a "sweeping" software that would scan customer accounts for a positive credit and simply wipe it off their account, transferring the money to Citibank's general account. This wasn't just a small thing either -- it went on for more than a decade, and the whistleblower who brought it up was fired.