A data unit for transmitting data in a digital broadcasting system includes a first payload field, and a first byte code field having a value indicating an offset of data in the first payload field with respect to an absent value. A method for formatting the data unit includes: providing data for a payload field for a data unit, wherein the data includes an absent byte value, determining an offset between an absent byte value and other data in the payload field, shifting the data in the payload field by the offset to produce shifted bytes, and inserting a byte code in the data unit, wherein the byte code indicates the offset. A transmitter for transmitting the data units, and a receiver for receiving the data units are also provided.