Here in Canada, by Jan 2007, the check number will have to be part of the MICR data. It is optional now, but will be mandatory by the end of next year. There is a mandatory date format and location as well as a specific placement of the amount field(s).
Right now I preprint the MICR data without check number, and assign the number at runtime, still with no MICR check number. It looks like I will have to assign the check number when the MICR is printed. Not as convenient, but I guess I'll have to live with it.
I use a LJ4 for checks, and as I recall, the MICR cartridge was about the same price as a regular one. I bought it from a cartridge refiller who happens to be across the street from the office. It may be worth shopping around.
The changes to the check specification are to do with the banks scanning them(OCR I guess) into digital format. Whether any of this will come to the US, I don't know.
Jim Asman