The single most important criteria for printing checks and other financial documents is their detectability by the machines that read the information off of them and verify them automatically. In the example of checks, you can see check readers at retails stores, supermarkets, and of course, at the banks. The technology that makes this possible is magnetic ink/toner. Instead of regular black toner inside of a cartridge, magnetic toner is used so that the characters on the printed checks can be scanned by the bank machines. A MICR toner cartridge is just like a regular toner cartridge, except that it contains specially formulated toner containing magnetic properties. Since each laser printer is different, one cannot simply use an universal MICR toner for another machine. Just like regular toners, which has a different formulation from machine to machine, MICR toner cannot be shared between different cartridge/machine types.

MICR toner is sometimes referred to as, MICRO toner, MICR laser toner, toner MICR, etc. When you need to acquire MICR toner, you would typically find them at MICR toner suppliers either locally or online. Remember that bulk MICR toner or bulk universal MICR toner do not exist, so make sure you do not attempt to refill your cartridges with untested MICR toners or even regular toners for that matter, to avoid getting unscannable checks, or worse yet, possibly damaging your machine. Every machine has a unique way it prints, requiring unique sealing temperatures, electrical charges, and many other factors on the MICR toner (same concept applies to regular toner).

Some of the most popular brands of machines and toner that have MICR toner available are Brother MICR toner, Lexmark MICR toner, and more.

For most applications, you do not need special MICR toner printers in order to print checks. All you need is a working laser printer that has MICR toner cartridges available for it. Occasionally, you will see companies selling specially modified printer just for check/MICR printing. These machines usually come with more advanced features such as a large number of built-in fonts, extra memory, etc., for professional and large print jobs.