MICR Toner Cartridges are required when printing checks. MICR stands for Magnetic Ink Character Recognition. MICR Toner cartridges contain a higher concentration of iron than regular cartridges, which allows you to print bank checks using your current laser printers. The magnetically charged iron particles printed on the checks allow bank equipment to properly scan and process the checks automatically. Without the use of MICR Toner cartridges, your checks will need to be entered manually by a teller and can be subject to bank processing fees.