MICR Line Decoder
Paste the MICR line from the bottom of a check and this tool separates out the routing number, account number, and check number, then validates the routing checksum. Everything runs in your browser, so the check data never leaves your computer.
It is built for anyone keying check details into a positive pay or check issue file who wants to confirm they grabbed the right field from the right part of the line.
What the MICR line is
MICR stands for Magnetic Ink Character Recognition. It is the row of stylized numbers and symbols printed in magnetic ink along the bottom edge of a check, in the E-13B font that bank equipment reads. The line carries the three pieces of information that identify the check: the routing number, the account number, and the check number (also called the serial number).
Those pieces are separated by four special symbols, often remembered as TOAD: Transit, On-us, Amount, and Dash. The transit symbols bracket the 9-digit routing number, the on-us symbols mark the field that holds the account number and often the check serial number, and the amount field on the far right is left blank until the check is deposited.
How the decoder reads the line
When MICR symbols are transcribed to a keyboard, the special characters are usually typed as letters or punctuation. The decoder looks for the transit-bracketed group to find the 9-digit routing number, reads the on-us field for the account number, and identifies the check serial number. Because layouts differ between personal and business checks, it labels each field so you can confirm the split is correct.
It also runs the routing number through the official ABA check-digit formula, the same 3, 7, 1 weighted test our generator relies on, so a transposed routing digit is caught immediately. A failed checksum is a strong signal that the line was read or typed wrong.
Why this matters for positive pay
A positive pay file is only as good as the check details inside it. The bank matches each presented check against your issue file by check number, account, and amount, so a wrong account number or a misread check number creates exceptions you have to clear by hand, or worse, lets a bad check slip through unmatched.
Decoding the MICR line correctly gives you clean, verified values to drop into the right columns of your file. The positive pay file format reference shows which field each value belongs in, and MICR line and positive pay walks through how the line ties into the matching process. For the bigger picture, see what is positive pay.
Tips for accurate decoding
- Personal vs business checks differ. Standard personal checks usually run routing, then account, then check number. Many business checks lead with the check number on the far left, so confirm the labels match what you expect.
- Watch the dash and on-us symbols. The account field can include a dash or internal bank codes. Strip those out before placing the account number in your file.
- Ignore the amount field. On an unwritten check the far-right amount field is empty. It is filled in only when the check is processed for deposit, so it is not part of your issue file.
- Trust the checksum. If the routing number fails the check-digit test, recheck the line before using any value from it.
Frequently asked questions
What is the MICR line on a check?
It is the row of numbers and symbols printed in magnetic ink along the bottom of a check, in the E-13B font. It encodes the routing number, account number, and check number so bank equipment can read the check automatically.
How do I read routing, account, and check numbers from the MICR line?
The 9-digit routing number sits between the two transit symbols on the left. The account number is in the on-us field next to it, and the check or serial number is nearby. This decoder labels each field for you and handles the different personal and business check layouts.
What do the MICR symbols mean?
There are four E-13B symbols, often remembered as TOAD: Transit brackets the routing number, On-us marks the account and serial field, Amount frames the dollar amount on the right, and Dash separates parts of the account field. They tell machines where each field begins and ends.
Why does the decoder check the routing number?
To catch misreads and typos. The routing number has a built-in check digit calculated with a 3, 7, 1 weight pattern. If the decoded routing number fails that test, the MICR line was almost certainly read or entered incorrectly.
Does the MICR line include the check amount?
Not on a blank or unwritten check. The amount field on the far right is left empty and is encoded only when the check is deposited and processed. It is not a value you use in a positive pay issue file.
Is my check data kept private?
Yes. The decoder runs entirely in your browser. The MICR line you paste is never sent to a server or stored, so your check details stay on your own computer.