A method and apparatus for verification of a voucher after printing by a gaming printer. A human readable validation character string is received by a printer controller for printing on a voucher. A scanned validation character string is read from the voucher using an optical recognition process as the voucher is being printed. The voucher is verified by comparing the received and scanned validation character strings. If the two validation character strings are different, the voucher may be voided by the printer controller before the voucher is finished being printed.