A Major Automated Information System (MAIS) is a defense acquisition program for an Automated Information System (AIS) that meets Acquisition Category (ACAT) IA requirements listed below. An AIS is a system of computer hardware, computer software, data, and/or telecommunications that performs functions such as collecting, processing, storing, transmitting, and displaying information.
A MAIS is determined for an acquisition program for an Automated Information System (either as a product or a service) that is either:
- Designated by the Milestone Decision Authority (MDA) as a MAIS; or
- Estimated to exceed:
|Acquisition Category||Reason for ACAT Designation||Decision Authority|
|ACAT IA1,2||MAIS (10 U.S.C. 2445a (Reference(n))): A DoD acquisition program for an Automated Information System4 (AIS) (either as a product or a service5) that is either:
MDA designation as special interest1
|ACAT IAM: DAE or as delegated
ACAT IAC: Head of the DoD Component or, if delegated, the CAE (not further delegable)
An EA is normally associated with MAIS acquisition programs. DoD Instruction 5000.02, Enclosure 4, Table 2-1, requires that an Economic Analysis be performed in support of the Milestone A, Milestone B, and Full-Rate Production Decision (FRPD) (or equivalent) reviews for MAIS. The purpose of the EA is to determine the best AIS program acquisition alternative, by assessing the net costs and benefits of the proposed AIS program relative to the status quo. In general, the best alternative will be the one that meets validated capability needs at the lowest Life-Cycle Cost (LCC) (measured in net present value terms), and/or provides the most favorable return on investment. 
For a MAIS program, consultation with the office of the Assistant Secretary of Defense for Networks and Information Integration (OASD(NII)), Office of Deputy to the ASD(NII) for Command, Control, Communications, Intelligence, Surveillance and Reconnaissance and Information Technology Acquisition is recommended, unless the Under Secretary of Defense (Acquisition, Technology & Logistics [AT&L] ) has retained authority for the program. 
The DoD Components are required to establish or employ decision bodies with similar responsibilities for Defnse Business System (DBS) that do not meet the MAIS threshold.
AcqLinks and References:
-  Defense Acquisition Guidebook (DAG)
- DoD Directive 5000.01 “Defense Acquisition System”
- DoD Instruction 5000.02 “Operation of the Defense Acquisition System”