We thought about it and decided to give it a try. Six months later we were still fooling with it. It turned out to be quite difficult but we finally succeeded and now have a font that's in use in several banks. When MICR technology was first developed in 1958 character recognition was VERY crude. Character recogntion has made huge strides since then.
Readers can actually reliably read a zero even if half of it is missing.
That's a lot of money. To help cure the problem, readers still use magnetic but if the check does not read magnetically, an optical reader takes over. The result is that virtually any MICR line printed with black ink is probably going to clear the system so you don't need MICR toner in a laser printer even though we still recommend it. The bank doesn't really care where your checks come from. Every time they touch a check it costs them money unless it's part of a big stack of checks.