| THE Leprosy Mission Northern Ireland | Health & social care | 2016 |
| THE Light Guys Ltd | Construction | 2020 |
| THE Little Learning Centre Ltd | Hospitality | 2024 |
| THE Margaret Finley Trust | Education | 2017 |
| THE Musician Academy Ltd | Education | 2020 |
| THE Nail Bar Lisburn Ltd | Other services | 2022 |
| THE Oaks (Bryansford) Management Limited | Households | 2023 |
| THE Old Boatyard Management Company Limited | Construction | 2010 |
| THE Pandm Market Limited | Wholesale & retail | 2025 |
| THE POD Pantry Ltd | Agriculture & fishing | 2026 |
| THE Professional Tree Company NI Limited | Administrative & support | 2017 |
| THE Resurgam Community Development Trust Limited | Information & communication | 2011 |
| THE Right Key (Lisburn) Community Interest Company | Information & communication | 2012 |
| THE Right Protection 4U Limited | Financial services | 2016 |
| THE Roast Works Ltd | Transport & logistics | 2020 |
| THE Salon Thing Ltd | Wholesale & retail | 2023 |
| THE Sanctuary NI Group Limited | Other services | 2019 |
| THE Schools Tennis Project Limited | Arts & recreation | 2003 |
| THE SOY Sauce Bistro 149 Limited | Hospitality | 2024 |
| THE Undie Factory Limited | Wholesale & retail | 2011 |
| THE Winter Garden Group Ltd | Wholesale & retail | 2021 |
| THE World and ME Ltd | Education | 2025 |
| Thermalfill Insulation and Remediation Services Ltd | Construction | 2025 |
| Think Bigger Marketing Limited | Professional & scientific | 2026 |
| Think Storage Limited | Transport & logistics | 2024 |
| Thomas John Ltd | Real estate | 2014 |
| Thomas John RD Ltd | Real estate | 2002 |
| Thompson Poultry Limited | Agriculture & fishing | 2016 |
| Thompson Renewables (Enniskillen) Ltd | Energy | 2016 |
| Thompson Renewables (Omagh) Ltd | Energy | 2016 |
| Thompson Services Ltd | Manufacturing | 2026 |
| Thorcaill Limited | Real estate | 2012 |
| Thorndale (Belfast) Ltd | Financial services | 2016 |
| Three Crowns Bar Ltd | Hospitality | 2016 |
| Three Homes Limited | Construction | 2019 |
| Three's Theatre Company Ltd | Arts & recreation | 2017 |
| TIA Tammy Ltd | Transport & logistics | 2020 |
| Tiad Management Ltd | Real estate | 2026 |
| Ticket Solutions LP | | 2018 |
| Tile and Grout Solutions Ltd | Manufacturing | 2021 |
| Titanic City Properties Ltd | Real estate | 2026 |
| Titanic Tattoo Ltd | Other services | 2014 |
| TJA Supplies Limited | Agriculture & fishing | 2017 |
| Tjhft Limited | Professional & scientific | 2012 |
| TK Motors Car Accident & Repair Centre Limited | Wholesale & retail | 2013 |
| TMJ Financial Services Ltd | Financial services | 2022 |
| TMW Aerospace Ltd | Professional & scientific | 2018 |
| Toddler Sense South NI Ltd | Education | 2022 |
| Togetfory Ltd | Wholesale & retail | 2026 |
| Toland House Properties Limited | Construction | 1982 |
| Toland Investments Limited | Extraterritorial | 2013 |
| Toloei Advanced Solutions Ltd | Wholesale & retail | 2025 |
| TOM Browne Limited | Real estate | 1997 |
| TOM Morrison Limited | Arts & recreation | 2018 |
| Tommygunn Tattoos Ltd | Arts & recreation | 2018 |
| TOO Much Hassle Ltd | Arts & recreation | 2024 |
| Top Asset Holdings Limited | Professional & scientific | 2020 |
| Top HAT Bingo Downpatrick Limited | Arts & recreation | 2014 |
| Top Trees Solutions Ltd | Administrative & support | 2025 |
| Topaz Properties Limited | Real estate | 2015 |
| Tophat Bingo Lisburn Ltd | Arts & recreation | 2015 |
| Toptech Capital (UK) Limited | Information & communication | 2017 |
| Torch Energy Consulting NI Limited | Professional & scientific | 2025 |
| Total Haulage Limited | Transport & logistics | 1990 |
| Touch Down Take OFF Ltd | Professional & scientific | 2023 |
| Toutes LES Boules Ltd | Hospitality | 2015 |
| Town's Gate LLP | | 2018 |
| TP KBB Ltd | Wholesale & retail | 2012 |
| Track KIT Ltd | Wholesale & retail | 2020 |
| Trade Copiers NI Limited | Wholesale & retail | 2021 |
| Tradehut Ltd | Wholesale & retail | 2020 |
| Trahj Ning Ltd | Wholesale & retail | 2025 |
| Training Soccer Limited | Other services | 2011 |
| Transformation Centre | Other services | 2013 |
| Travel Study Ireland Ltd | Administrative & support | 2016 |
| Trebornaillig Limited | Real estate | 2013 |
| Treewiseni Limited | Financial services | 2018 |
| Trench Control NI Limited | Construction | 2010 |
| Trillium (2015) Ltd | Manufacturing | 2015 |
| Truck & Plant Hire Limited | Administrative & support | 2018 |
| Truck BUS & Trailer Components Ltd | Wholesale & retail | 2011 |
| Trustees of the Reformed Presbyterian Church of Ireland | Other services | 1930 |
| Tscl Projects Limited | Construction | 1999 |
| Tsm-Aero Limited | Manufacturing | 2023 |
| Tullyard Developments Ltd | Construction | 2020 |
| Tullydevenish Holiday Park Limited | Hospitality | 2015 |
| Tullynewbank Stables Limited | Agriculture & fishing | 2004 |
| Tulnax Ltd | Construction | 2016 |
| Turkish Kebabs Lisburn Ltd | Hospitality | 2025 |
| Turner Grain Engineering (Ireland) Limited | Manufacturing | 2005 |
| TW Braga in the Community | Arts & recreation | 2016 |
| TW Braga Limited | Arts & recreation | 2013 |
| Twin Oaks Orthopaedics Limited | Health & social care | 2022 |
| Twinz Grills Ltd | Hospitality | 2024 |
| Tyrone House Limited | Professional & scientific | 1996 |
| UCG - United Capital Group LLP | | 2025 |
| UK Disposable Vape Ltd | Wholesale & retail | 2023 |
| UK Finantech Holdings Limited | Professional & scientific | 2020 |
| Ukrainian Construction Company (2024) Ltd | Construction | 2024 |
| Ulelasting Limited | Wholesale & retail | 2024 |