Canadian Imperial Bank of Commerce will refund about $27 million to about 200,000 clients who were overcharged on some borrowing transactions dating back to 1993.

The bank said the majority of the refunds will go to clients who were overcharged for certain overdraft fees. Refunds will also be paid to clients for adjustments on mortgage charges, interest on business account overdraft facilities, or mortgage life insurance premiums.

In cases where clients were undercharged, CIBC will not be seeking reimbursement.

"We apologize for any inconvenience this situation has created and want to assure our clients that the cause of these errors has been corrected," said Raza Hasan, senior vice-president at for CIBC mortgages, lending and insurance. "We have conducted a comprehensive review of all client accounts that might be affected, and are initiating refunds for these clients," Hasan said.

Beginning Friday, clients will start getting automatically refunded by electronic funds, transfer or cheque, and notified by letter. The bank also said it will launch a client notification program to inform current and former clients how to apply for a refund.