A method of printing a modified product code includes providing a printer and a substrate. An initial product code is determined. The initial product code includes a plurality of unmodified characters. A modified product code is determined. The modified product code includes at least one modified character that is different from a corresponding one of the plurality of unmodified characters of the initial product code. The modified character is a function at least in part by of initial product code. The printer is controlled to print the modified product code on the substrate.