Many states require income tax returns to incorporate two-dimensional (2D) barcodes on forms. These 2D barcodes contain more information than conventional barcodes you see on retail packages. Conventional barcodes get wider as more data is encoded, while 2D barcodes make use of the vertical dimension for data. These barcodes contain all pertinent tax information from your return and are scanned by computers with the IRS or state tax agency.