There are three major pieces of technology involved when a check reader performas a check scan: digital-light scanning, handwriting-analysis software and interpretation of the data on the MICR line. After a check has passed through these technologies, it is sent for deposit in a person’s account.

Performing a Digital Scan

Modern technology has made check scanners capable of capturing a digital image of a check.

A check-scanning device scans the front and back of a check and creates a digital image. A check scanner uses light detectors that pass over the check and pick up on contrasts between light and dark, such as the contrast between pen ink and the paper’s surface.

It’s these contrasts that help to adequately create a digital image that replicates what the check's appearance.

Using Handwriting Technology

The technology behind check-scanner machines has sufficiently advanced so that even a person’s handwriting can be interpreted by the scanners, though this is the trickiest part of the scanning process. Between any given two people, handwriting can be extremely different, so the handwriting-scanning technology on a computer needs to be fairly sophisticated.

The detection of a person’s handwriting is done using the same light-scanning process that creates the digital image, though this is only the first step in interpreting the writing.

After the scanner has identified a person’s handwriting on the check while creating the digital image, the image of the handwriting is passed through a software scan. This scan analyzes the image and identifies what the person wrote, including their name, the amount deposited and signature.

Handwriting software is sufficiently sophisticated that it can interpret multiple variations of handwriting. Once the handwriting has been compared against the software’s database of handwriting, the amount written on the check is sent for deposit.

The MICR Line

The first technology that check readers rely upon is Magnetic Ink Character Recognition, or MICR. A check’s MICR code or MICR line is written out at the bottom of a check and typically includes the associated routing number, account number and check number.

This line on a check is printed in a way that allows computers to read that specific line easily and process the information printed on the paper. This is among the oldest technologies used on checks and has been used for decades.

While the ink used on the MICR line makes the scanning process easier, the font also eases the process. MICR lines are printed in one of two specific fonts in order to ease the scanning. Because the MICR line is printed in a special ink, a scanner can read that line even if it’s been written over with a signature or other marks.

When scanners read the MICR line, they identify the routing number to identify the bank from which the money will be drawn, as well as the account number that specifies the account.

Putting It All Together

From start to finish, the scanning process works like this.

A person scans the check, which passes through a light scan that detects contrasts in the ink. This contrast in light is used to create a digital image, and the handwriting sections of that image are passed through software for analysis. The MICR line is used to identify the bank and account the money will be coming from.

During this process, if any of the data is found to be invalid - because of a bad routing number, for example - the check is rejected. Otherwise, the money is deposited.

Traditionally, this process required a banking machine to complete. Advances in mobile technology have made it possible for check-scanner apps to complete a similar process using mobile devices, which rely on their cameras to capture the same information, down to the MICR line, as a traditional check scanner.