This standard establishes the construction, layout, data elements, data content, and printing specifications for Image Replacement Documents (IRD). An IRD is a substitute image copy of a check or a replacement for a previous IRD that includes a machine readable MICR line. An IRD may under certain legal arrangements be the practical and legal equivalent of the original paper check or a previous IRD. An IRD conforming to these specifications may be used as a Substitute Check in conformance with the Check Clearing for the 21st Century Act (Check 21 Act or Act). This standard does not address operational, implementation, or settlement issues. These issues may include but are not limited to: the use of security features that are available after imaging, image compression, conversion methods, and IRD printing techniques. The informative annexes attached to this standard provide information that may prove useful to those planning on implementing the standard.