| Advanced Systems Concepts, Inc. | 1469540 | 2024-12-20 | Active | Madison |
| Advanced Systems Consulting LLC | 1095029 | 2016-06-14 | Dissolved | Madison |
| ADVANCED SYSTEMS DESIGN, INC. | 712375 | 2002-01-30 | Withdrawn | Oxford |
| ADVANCED SYSTEMS DESIGN, INCORPORATED | 668054 | 1999-03-11 | Dissolved | Clinton |
| ADVANCED SYSTEMS ELECTRONICS, INC. | 511964 | 1983-09-26 | Dissolved | — |
| ADVANCED SYSTEMS INC. | 523383 | 1985-06-21 | Dissolved | Meridian |
| ADVANCED SYSTEMS INTERNATIONAL, INC. | 561891 | 1989-03-08 | Dissolved | JACKSON |
| ADVANCED SYSTEMS TECHNOLOGIES, INC. | 680914 | 1999-12-15 | Canceled | Gulfport |
| Advanced Systems Technology LLC | 1096878 | 2016-07-13 | Active | Madison |
| Advanced Systems, Inc. | 939525 | 2008-10-13 | Active | Jackson |
| ADVANCED SYSTEMS, INC. | 130775 | 1977-08-11 | Dissolved | — |
| Advanced Tactical Ordnance LLC | 964241 | 2010-04-02 | Active | Abbeville |
| Advanced Tactical Services LLC | 881687 | 2005-11-17 | — | Gulfport |
| Advanced Tech Heating & Cooling LLC | 1046087 | 2014-08-04 | Dissolved | Jackson |
| Advanced Tech Services LLC | 1352543 | 2022-08-09 | Active | Gulfport |
| Advanced Tech Solutions LLC | 1167916 | 2019-02-06 | Dissolved | Oxford |
| ADVANCED TECHNICAL CURRICULUM, INC. | 712830 | 2002-02-11 | Dissolved | BRANDON |
| Advanced Technical Services LLC | 1053806 | 2014-10-17 | Dissolved | byram |
| ADVANCED TECHNICAL SERVICES, LTD. | 553683 | 1987-08-17 | Dissolved | PEARL |
| Advanced Technologies and Installation Corporation | 876096 | 2005-08-02 | Canceled | Madison |
| Advanced Technologies Applications LLC | 945135 | 2009-02-18 | Dissolved | Vicksburg |
| ADVANCED TECHNOLOGIES INC. | 851677 | 2003-07-21 | Dissolved | Jackson |
| ADVANCED TECHNOLOGIES INTERNATIONAL, INC. | 621757 | 1995-09-01 | Revoked | LEXINGTON |
| Advanced Technologies Manufacturing LLC | 979963 | 2011-03-11 | Active | Vicksburg |
| ADVANCED TECHNOLOGIES, INC. | 511386 | 1983-08-22 | Dissolved | — |
| Advanced Technology Advisory Services, LLC | 1223333 | 2020-07-13 | Active | Gulfport |
| Advanced Technology Building Solutions, LLC | 923673 | 2007-12-10 | Active | Jackson |
| ADVANCED TECHNOLOGY CONNECTIONS INC. | 651518 | 1998-01-13 | Dissolved | — |
| ADVANCED TECHNOLOGY CONSULTING, INC. | 696394 | 2001-01-09 | Dissolved | — |
| ADVANCED TECHNOLOGY GROUP, INC. | 611047 | 1994-09-26 | Dissolved | HIGHLAND VILLAGE JACKSON |
| Advanced Technology Innovations LLC | 1439087 | 2024-04-19 | Active | RIDGELAND |
| ADVANCED TECHNOLOGY LABORATORIES, INC. | 580022 | 1991-04-29 | — | Madison |
| ADVANCED TECHNOLOGY LABORATORIES, INC. | 651749 | 1991-04-29 | Canceled | — |
| ADVANCED TECHNOLOGY LOGISTICS, INC. | 1141626 | 2018-03-14 | Revoked | JACKSON |
| Advanced Technology Logistics, Inc. | 1436105 | 2024-04-01 | Active | JACKSON |
| Advanced Technology Modular, LLC | 939877 | 2008-10-20 | Active | Jackson |
| Advanced Technology Resources, Inc. | 948708 | 2009-04-29 | Dissolved | Florence |
| ADVANCED TECHNOLOGY SECURITY SYSTEMS, LLC | 635228 | 1996-10-18 | Dissolved | — |
| Advanced Technology Services, Inc. | 979946 | 2011-03-11 | Active | Madison |
| ADVANCED TECHNOLOGY SERVICES, INC. | 655859 | 1998-04-30 | Withdrawn | Gulfport |
| Advanced Technology Solutions, Inc. | 620626 | 1995-07-26 | Merged | — |
| Advanced Technology Systems Company, Inc. (of Virginia) | 938405 | 2008-09-19 | Dissolved | Ocean Springs |
| ADVANCED TECHNOLOGY SYSTEMS GROUP, LTD. | 632508 | 1996-07-29 | Dissolved | — |
| ADVANCED TECHNOLOGY, INC. | 130776 | 1972-04-04 | Dissolved | — |
| ADVANCED TECHNOLOGY, INC. OF DELAWARE | 566310 | 1989-09-15 | Revoked | Wilmington |
| Advanced Tel, L. L. C. | 978365 | 2011-02-09 | Active | Madison |
| ADVANCED TEL., INC. | 638904 | 1997-02-11 | Canceled | Gulfport |
| ADVANCED TELCOM GROUP, INC | 682006 | 2000-02-03 | — | SATA ROSA |
| ADVANCED TELCOM, INC. | 689930 | 2000-02-03 | Revoked | SATA ROSA |
| ADVANCED TELE COMMUNICATIONS, INC. | 571660 | 1990-04-27 | Dissolved | TUPELO |