MICR (Magnetic Ink Character Recognition) is the line of numbers at the bottom of a check that banks use to process it by machine. Getting this right matters more than any other part of the check — a check with wrong or missing MICR encoding may not process correctly even if it looks fine visually.
What the MICR line needs
- The correct font — a standardized typeface called E-13B, not a regular monospace or "bank-style" font that just looks similar.
- Correct positioning along the bottom edge of the check, within a specific margin defined by ANSI X9 standards.
- The right content and order: check number, then routing number (bracketed by a transit symbol), then account number.
Is self-printed MICR legal?
Yes. Self-printed checks with MICR encoding are legal under the Check 21 Act and the Uniform Commercial Code in the US, as long as they meet the ANSI X9 formatting standards. Most major banks accept them through standard processing. Acceptance can still vary slightly by institution, so it's worth confirming with your bank if you've never printed your own checks before.
This is the core technical problem Check Writer 123 solves — it generates correctly formatted and positioned MICR encoding automatically, so you don't have to source a MICR font or calculate margins yourself.