An User-Defined Accounting Key (UDAK) is a common term in accounting. It refers to the customized Accounting Key used by an enterprise to define out their accounts. An example of this would be how a retail store chain may use the UDAK of Entity, Division, Region, District, Store, Department, and Account; while, a hospital might use Entity, Department, Account, Physician, and Patient Type.
The UDAK of an enterprise is the most insightful and annoying part of Information Services (IS) to deal with. Every system that touches money must be customized to use the UDAK.