
Check 21
First enacted on October 8, 2004, the 21st Century Act (also known as the Check 21 law) allows banks to handle more checks electronically, eliminating much of the effort needed to transfer checks between banks physically. Check 21 is responsible for an interesting precedent that was rarely considered prior to its creation: the use of remote deposits.
Specifically, Check 21 allows for the creation of a “substitute check,” a high-quality representation of both sides of a check, which legally acts as the original. This method is far quicker and efficient than the exchange of physical checks. Clearly, because of the high importance of something that legally serves as monetary value, there was a need to quickly standardize the structure and exchange of check images. This task that was embarked upon by Accredited Standards Committee X9 (ASC X9), an ANSI accredited standards developing organization devoted to the financial industry.
ANSI X9.100-187 Development and Mobile Deposit Growth
Even before the law was enacted, X9 had approved the Draft Standard for Trial Use for check images as DSTU X9.37–2003. After using this as the standard for all major check image exchanges for some time, ANSI X9.100-187–2008 was published, incorporating improvements based off practical industry knowledge.
Since the 2008 publication, the usage of check images has grown due to the advancement of computers and smart phones. Mobile deposits have become far more of a common practice in recent history, and the COVID-19 pandemic may have provided further acceleration for their everyday adaptation. Of the customers who used mobile deposits in 2020, 42% did so for the first time. In fact, 70% of all customers prioritize mobile deposit in the list of banking capabilities they look for. One survey even reported that 90% of respondents were depositing their money through their financial institution’s app.
The latest revision of the standard for check image exchange, ANSI X9.100-187-2021: Electronic Exchange of Check and Image Data was created to meet the current needs of the industry.

About ANSI X9.100-187-2021
ANSI X9.100-187-2021 establishes the basis for check image exchange for financial institutions in the United States, setting guidelines and limitations reflective of current industry practices while remaining fluid enough to accommodate the needs of varying networks and institutions.
The standard sets the file sequences, record types, and field formats to be used for the electronic exchange of check MICR (magnetic ink character recognition) line, associated check processing data, and check images in the form of cash letters. The goal of this document is to facilitate the exchange of electronic check data for forward check presentment, IRD creation, customer deposit, return item notification, and returns processing through a shared structure.
ANSI X9.100-187-2021 makes use of hierarchical record types to structure a file in a manner similar to a physical cash letter. The specific file structure is thoroughly addressed in the comprehensive content of the primary document and its 12 annexes.
Users of the ANSI X9.100-187-2021 standard should note that the document does not address operational, implementation, or settlement needs, which are important for its actual application. Despite this, the standard user will have to make choices for data and image compression, encryption, and transmission specifications. However, the informative annexes of the document do provide information that should be useful for such requirements.
Users of this document should also be aware that most financial exchanges utilize a “companion document” that defines the specific rules for exchange within a particular network. The companion document should reference the relevant version of this standard.
Changes to ANSI X9.100-187-2021
ANSI X9.100-187-2021 revises the 2016 edition of the same American National Standard for the electronic exchange of check and image data. In addition to some minor changes made throughout the document, this new edition:
- Updated definitions, including those for electronic check, electronic check exchange (ECE), electronically-created item (ECI), external processing code field (EPC), payor, short name, truncation, and right and left justification
- Changed name and expanded usage of Archive Type Indicator to include Capture Source in the Check Detail Record (Type 25) and Return Record (Type 31)
The changes made to every edition of ANSI X9.100-187 are outlined in Annex L of the standard.
ANSI X9.100-187-2021: Electronic Exchange of Check and Image Data is available on the ANSI Webstore. It and related standards are available together as the Check Image Exchange Basics Collection.