Data Capture (a/k/a Draft Capture): The collection, formatting, and storage of information in computer memory. Some point-of-sale terminals perform data capture functions. See EDC Terminal.
Data Encryption Key (DEK): Used for the encryption of message text and for the computation of message integrity checks (signatures).

Data Encryption Standard (DES): A popular standard encryption scheme.

Database: A collection of data organized and designed for easy access i.e., a collection of customer names and addresses.

Debit: A charge to a customer's bankcard account.

Debit Transaction: A bankcard used to purchase goods and services and to obtain cash, which debits the cardholder's personal deposit account.

Demand Deposit Account (DDA): Usually abbreviated as DDA, it refers to the merchant bank account the payment processor credits or debits for deposits, fees and adjustments.

Deposit Credit: See Credit Deposit.

Dial-Up Line: A communications medium described as a non-dedicated telephone line, in which a connection is established by dialing a destination number and broken when the call is complete. This is the same type of phone line that you use at home.

Dial-Up Terminal: An authorization terminal that (like a telephone) dials the authorization center for validation of transactions.

Direct Marketing: A transaction category for providing customized services and procedures for merchants which offer merchandise or services via catalogs, telephone calls, mailings, and/or advertisements.

Direct Payment: A method of collection used in the ACH network for certain claims, generally those that are repeated over a period of time, under which the debtor gives the originator a standing authorization to debit his or her account.

Disclosure: The information required by federal or state law to be relayed to the cardholder concerning the terms of the credit agreement. Disclosure must be made by the issuer before the first use of the card by the cardholder, and must subsequently be included on all monthly statements and other documentation mentioning finance charges.

Discount Rate: An amount charged a merchant for processing its daily credit card transactions.

Doing Business As (DBA): Refers to the specific name and location of the merchant establishment where credit card purchases are made.

Domain Name System (DNS): A general-purpose data query service whose principal use is the lookup of host addresses based on host names. Important domains are .com (commercial), .edu (educational), .net (network), .gov (U.S. government), .mil (U.S. military) and .org (organization).

Down Time: A period when all or part of a system or network is not available to end users due to failure or maintenance.

Download: To copy a file from a remote computer 'down' to your computer.

Duality: The membership of a financial institution in both MasterCard and VISA. Legality outside of the U.S. varies according to nation.