Computing error caused by switching the position of two adjacent digits. Since the resulting error is always divisible by 9, accountants use this fact to locate the misentered number. For example, a total is off by 72, dividing it by 9 gives 8 which indicates that one of the switched digit is either more, or less, by 8 than the other digit. Hence the error was caused by switching the digits 8 and 0 or 1 and 9.