Checksum
If 000201231234567890154 (the bank account number without the dots) is divided by 97, the answer is 207458809978249 remainder 1. Since the remainder is "1", the bank account identifier is probably correct. If the person writing down the number missed a digit, swapped two digits around or wrote a digit down incorrectly the remainder would not have been "1". If this is the case then the computer should detect an error and give an error message.