The check digit is the result of mathematical calculations that are used to verify the accuracy of the account number. Currently the IP Dept supports ten different Check Digit Routines (CDR). Each CU is allowed to have two different CDRs set if needed.

Any account number that does not fit the established CDR for the CU will become a rejected check and will have to be keyed manually by IP staff. The CDR helps reduce the number of invalid account numbers on the CU exception report and also provides the IP staff with insight on our sorters ability to accurately read the MICR line of a check.