MICR Line Decoder

What Is a MICR Line?

The MICR (Magnetic Ink Character Recognition) line is the string of characters printed in magnetic ink at the bottom of checks. It uses the E-13B character set — 10 numeric characters (0–9) plus four special symbols: transit (⑆), on-us (⑈), amount (⑇), and dash (⑉). High-speed check sorters in bank operations read this line magnetically rather than optically, which is why the ink composition matters as much as the character shapes. The format has been standardized since the late 1950s and remains the backbone of check clearing worldwide.

MICR Field Layout

A standard MICR line contains three fields. The transit field (bracketed by ⑆ symbols) holds the 9-digit ABA routing number that identifies the paying bank. The on-us field (bracketed by ⑈ symbols) contains the account number and check number as defined by the paying bank — there is no universal format for on-us data, so layouts vary between institutions. The amount field (bracketed by ⑇ symbols) is optionally added by the bank of first deposit during processing. The routing number includes a check digit validated using the ABA 3-7-1 weighted sum algorithm, which this tool verifies automatically.

Check Processing Automation

MICR parsing is the foundation of check processing automation — remote deposit capture, positive pay file generation, exception item handling, and reconcilement. I build integrations between check capture systems, core banking platforms, and ERP accounts receivable modules that parse, validate, and route MICR data through the clearing lifecycle. See integration services, explore the NACHA/ACH Explorer and Positive Pay Generator, or get in touch.