The MICR Line is a clear band at the bottom of the check. Only the MICR characters can be printed within this clear band. The MICR Line has a clearly-defined format, according to ANSI standards. Any variations from these formatting requirements will cause the check to be rejected by the bank.
The MICR Line consists of four fields (positions indicated are from right to left):
1. Amount (positions 1 to 12)
2. On-Us (positions 14 to 31)
3. Transit (positions 33 to 43)
4. Auxiliary On-Us (positions 45 to 65)