Apparatus and method for authentication of postage accounting reports. Postage accounting report data is authenticated by first assembling authentication mark data from the postage accounting report data and encrypting the resultant information to form an authentication mark. A physical representation of that authentication mark is then affixed to a postage accounting report generated by a postage accounting report system. The postage accounting report may subsequently be authenticated by communicating the authentication mark to a responsible party (for example, a postal authority or manufacturer) for purposes of decrypting the authentication mark and authenticating the postage accounting report data using the decrypted information.