Check image exchanges include two key elements necessary to perform 1) the posting of check payments and 2) the normal compliment of day-two functions. These elements are the exchange of the MICR line on the check and the exchange of the check image.
Most organizations find it difficult, if not impossible, to post from a picture (image) of the check and rely on the MICR line for posting and on the image for other functions like signature verification and statement preparation. Since both information sets are used for different purposes and in different timeframes, sometimes it may be preferable to exchange the MICR and image information in two different files at two different times; e.g. the MICR line file in time for posting and the image file in time to perform the other functions. Alternatively, check images could be sent throughout the day with the MICR line file sent immediately prior to the DDA start time for posting.
When both sets of information are transmitted at the same time it may be preferable to have all of the information in the same file and sometimes it is better to have the MICR line information in one file and the images in a second file.
ECCHO's image exchange rules and the X126.96.36.1998 format standard both accommodate all of these various options for exchanging MICR line and image information.