| THE Glendalough Trust | Professional & scientific | 2006 |
| Thermomax Limited | | 1981 |
| Thompsons a to B Removals Limited | Transport & logistics | 2007 |
| Timber Enhancement Services Ltd | Extraterritorial | 2008 |
| Timothy Smyth Hair Design Ltd | Other services | 2004 |
| Tinnelly Construction Limited | Construction | 2002 |
| Tjlg Properties Limited | Administrative & support | 1999 |
| TMW Security Services Ltd | Construction | 2002 |
| Tomis Ltd | Extraterritorial | 2006 |
| Trans-Channel Services (Penrith) Limited | | 1994 |
| Tresses Limited | Health & social care | 2009 |
| Tridget Limited | Extraterritorial | 2004 |
| Trom Limited | Information & communication | 2000 |
| TT Homes Ltd | Construction | 2000 |
| TT Technologies Limited | Information & communication | 2004 |
| Tulivin Laboratories Limited | Professional & scientific | 1992 |
| Virginia Developments Limited | Construction | 1997 |
| Virtuoso CCC Ltd | Wholesale & retail | 2024 |
| Vision Information Consulting Limited | Information & communication | 1990 |
| Visual Narrative Ltd | Information & communication | 2004 |
| W. & R. Jacob & Co, (Northern Ireland) Limited | Professional & scientific | 1982 |
| W.Belshaw (Portadown) Limited | | 1976 |
| Walmur Developments Limited | Construction | 2007 |
| Walter Watson Limited | Manufacturing | 1975 |
| Warners Limited | Extraterritorial | 1939 |
| WG Contracts Limited | Construction | 2007 |
| Wgab Limited | Wholesale & retail | 2005 |
| William Keown Trust - the | Administrative & support | 1999 |
| William Mcallen & Sons Limited | Construction | 1969 |
| Willowbank Farm Limited | Extraterritorial | 1967 |
| XL Transport Ltd | Transport & logistics | 2013 |
| Xvii Hundreds Furniture Limited | Construction | 1983 |
| Yellow Moon Post Production Limited | Information & communication | 1996 |