The MICR line on a check, explained

The odd numbers along the bottom of a check are the MICR line. Banks use them to know who pays and which account. This page says where each piece goes, and what we did not measure.

Four symbols, then the digits

E-13B is the character set. Besides 0 through 9 it has four marks. A transit mark brackets the routing number. An on-us mark sits by the account, and on a business check it also brackets the serial number. An amount mark would wrap the dollar amount, but that field is left empty so the bank can encode it. A dash mark can appear inside an account number.

The governing layout document is ANSI X9.100-160-1. We do not own that standard, so the positions below follow public summaries of it (Morovia's placement guide and the MICR gauge notes at micrfonts.com), not a copy of the paywalled text. Treat them as our working rules, and check a printout before you depend on it.

Where the fields sit

• The clear band is the bottom 5/8 inch. Only the E-13B characters belong there. Borders, words, and the SAMPLE mark stop above it.
• Characters are 1/8 inch apart. Position 1 starts 5/16 inch in from the right edge. The baseline is 3/16 inch up from the bottom, inside a print band that is 1/4 inch tall.
• Positions 1 through 12 are the amount. We leave them blank.
• The routing number, with a transit mark on each side, occupies positions 33 through 43.
• On a personal check the account and the check number share the on-us area, which has room for 18 characters.
• On a business check the serial number moves to the auxiliary on-us field, to the left of the routing number.

The check maker draws those boxes at one size. The on-screen zoom is only a magnifying glass. It does not change the PDF.

How tall the characters are

We did not find a free primary source for the exact E-13B height. ANSI and ISO 1004 are paywalled, and the Payments Canada Standard 006 figures were not measured glyph by glyph for this page. The drawings we use are Zachary Schneider's, published under the SIL Open Font License 1.1, and he traced them from Standard 006. He says they have not been professionally tested. We have not put them on a MICR gauge either. The height you see is per our best public sources, scaled so each character still fits the 1/8 inch pitch and the 1/4 inch print band.

You can read the OFL license and the source SVGs (digits 0 to 9 and the four symbols, files u0030 through u0039 and u2446 through u2449). There is no separate font file to install. The check is drawn from the paths.

Magnetic ink, and an old statistic

12 CFR 229.2 describes this line as numbers printed in magnetic ink. In 2010 the Federal Reserve Banks estimated that 99.4 percent of their forward check deposits were already electronic images (Federal Register 75 FR 67731, Table 9, published November 3, 2010). That number is old. It is not a description of your bank this year. Image capture is why a plain-toner check often goes through, and it is also why some banks, including the Simmons Bank printing guide, still ask for MICR toner. Print a test. Ask them.

The checksum, briefly

The last digit of the routing number makes a weighted sum divisible by 10. The weights are 3, 7, and 1, repeated. A number can pass that test and still be the wrong kind of prefix. Paper-check prefixes in the ABA policy are 00, 01 to 12, 21 to 32, and 80. The home printing guide covers paper and alignment. Empty designs, with this line left off, are in the blank check templates.