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Explaining the "Fraction" on a Check

What does the fraction in the upper right corner of a check mean?

That fraction has been around for a long time. It used to be used to sort checks and route them to their paying banks back before the magnetic ink character recognition (MICR) symbols were adopted and check processing became automated.

The fractional routing number has three parts in the form of AA-BBBB/FFFF. The AA portion designates the city or state of the bank on which the check is drawn. The number 1-49 represent major cities as of 1900, in order of population (at the time, New York ranked first, Chicago second, etc.). The numbers 50 and up designated states and territories, starting with New York. In most cases, cities 1 - 9 (New York City through Detroit) are designated without a leading zero.

The BBBB portion designates a specific bank within the city or state. In many cases leading zeroes in both the city and bank numbers are not used, so that, for example, 5-39 is the number that used to be assigned to the old First National Bank of Boston (now part of Bank of America). The FFFF portion was used in routing checks to the proper Federal Reserve Check Processing branch for clearing. The first two characters (or one, for numbers 1 - 9) designated the Federal Reserve District of the bank on which the check was drawn. The digit 1 represented the First District, headquartered in Boston, the number 12 represented the Twelfth District, with headquarters in San Francisco. Until 1985, 20 was added to these two digits if the paying bank was a savings bank, savings and loan or credit union. Savings bank checks drawn in the Boston region had 21 (1 = 20) in that position; those in California had 32 (12 + 20). Those "thrift institution" numbers assigned through 1985 are still used by those banks or their successors, but the practice of assigning the special number range to thrifts has been abandoned since then for new numbers assigned since 1985. The last two digits in the FFFF pattern provided information on special routing arrangements, branch offices of the Federal Reserve district, etc. Two of the numbers from the fraction, the FFFF and BBBB portions, have survived the transition to MICR coding and automation. As an illustration, the numbers 53-574/113 appeared on checks drawn on Hyannis Trust Company (later Cape Cod Bank and Trust Company, and now part of TD Bank). The 53 designated Massachusetts, 574 indicated the bank itself, and 113 meant the bank was in the First District, outside the city of Boston, and in Massachusetts. Checks on that bank were MICR encoded with 011305749. Note that the first four digits originate from the FFFF portion of the fractional form, and 0574 come from the BBBB portion. The last digit (9) is mathematically derived from the first eight, and is used to ensure the digits have been read properly by the high-speed check processors in use today.

The fraction is a bit of a relic. It has no real use today, unless a check has been mutilated so that the MICR encoded routing information is illegible. Then the fraction, if legible, can be used to determine what the MICR numbers should be, and the check can be repaired for processing.

Published on 4/27/09