Business check MICR strings: why is the check number on the left?

Question

I have always seen the MICR string at the bottom of a personal check have the routing number, then account number, then check number. Why do business checks often have the check number on the left?

Answer 1

MICR fields are defined by their distance to the right edge of the check. The routing number is always the same distance from the right edge. Business checks are longer and have more room for auxiliary information on the left if the bank chooses to use it.