A temporary loss of money is sufficient to confer Article III standing. Here, defendant wrongly withheld $531 in state sales tax from plaintiff. Although defendant refunded those taxes, it did not pay plaintiff the $3 in interest that plaintiff claimed to be owed for the time defendant had withheld the sales tax. Loss of even a small sum of money (here, $3) is sufficient to confer Article III standing, as is a temporary (here, months-long) deprivation of a substantial sum ($531) of money. To prove injury sufficient for Article III standing, the plaintiff need not show she would have invested the money and earned interest on it. Interest is simply a way of measuring the value of the lost use of the money during its temporary deprivation. It is the deprivation that is the Article III injury, not the loss of interest that might otherwise have been earned.