| Thompson Consulting Solutions Limited | Professional & scientific | 2018 |
| Thornleigh Apartments (Bangor) Limited | Households | 1975 |
| Thrive-Metric Consultants Ltd | Health & social care | 2025 |
| Tile Works (N.I.) Ltd | Wholesale & retail | 2011 |
| Tileswoodfloorni Ltd | Wholesale & retail | 2021 |
| Tina’S Fastfood Ltd | Hospitality | 2024 |
| Tiptop Holdings Limited | Real estate | 2018 |
| TK Convenience Ltd | Wholesale & retail | 2023 |
| TLW Commercial Ltd | Administrative & support | 2018 |
| TLW Holdings Limited | Wholesale & retail | 2023 |
| Tobi & Co. Ltd | Transport & logistics | 2024 |
| Todd Chart Agency Limited | Wholesale & retail | 1990 |
| Together Leisure Group Ltd | Hospitality | 2026 |
| Toilet Association of Ireland Limited | Other services | 2006 |
| TOM Tax and Training Ltd | Financial services | 2022 |
| TOM Vousden Limited | Manufacturing | 2024 |
| Tonn Architecture Limited | Professional & scientific | 2021 |
| Top Cake Toppers Ltd | Wholesale & retail | 2021 |
| Toplocation 5 Limited | Real estate | 2016 |
| Toto & Co (Holywood) Limited | Administrative & support | 2023 |
| Totten & Connolly Limited | Health & social care | 2007 |
| Touch of Class Vaping Ltd | Wholesale & retail | 2021 |
| Tough Rack Depot Ltd | Wholesale & retail | 2020 |
| Tours and Tales NI Ltd | Administrative & support | 2025 |
| Tower Court Management (Conlig) Limited | Extraterritorial | 2002 |
| TPM Properties Lurgan Ltd | Administrative & support | 2025 |
| Trade Harmonizer Ltd | Administrative & support | 2023 |
| Trafford Street Chester Limited | Construction | 2017 |
| Transparent Film Limited | Administrative & support | 2017 |
| Treborth Golf Holdings Limited | Financial services | 2022 |
| Treborth Golf Limited | Arts & recreation | 2022 |
| Treborth Leisure Holdings Limited | Financial services | 2022 |
| Treborth Leisure Limited | Administrative & support | 1998 |
| Treborth Properties Limited | Real estate | 2022 |
| Treborth Property Holdings Limited | Financial services | 2022 |
| Trevor Brown Associates Ltd | Administrative & support | 2012 |
| Trewan House Trewan Sands Caravan Park Limited | Hospitality | 2017 |
| TRG Enterprises Ltd | Arts & recreation | 2026 |
| Tribe Creative Ltd | Wholesale & retail | 2024 |
| Triggon Ltd | Other services | 2021 |
| Trinsic Innovations Limited | Manufacturing | 2024 |
| Trinsic Vitality Limited | Manufacturing | 2024 |
| Triple a Lettings Limited | Real estate | 2021 |
| Triple-Z Logistics Limited | Wholesale & retail | 2025 |
| Troy International Ltd | Information & communication | 2015 |
| Tryfan Cabs Ltd | Transport & logistics | 2003 |
| Tubs 2 Pools Ltd | Construction | 2024 |
| Tudor Management Company Limited | Extraterritorial | 1986 |
| Turkis(H)Airways Balloo Ltd | Other services | 2022 |
| Turner Medical Services Limited | Health & social care | 2019 |
| Turner Towers Management Limited | Real estate | 2024 |
| Tuzzl Limited | Information & communication | 2019 |
| TW Roberts Properties Ltd | Real estate | 2025 |
| Two Guys Pizza Ltd | Hospitality | 2025 |
| TY Bach Anglesey Limited | Hospitality | 2024 |
| TY Capel Ltd | Real estate | 2022 |
| TY Caro CYF | Real estate | 2026 |
| TY Glyndwr Hotel & Su's Cocktail Bar Limited | Hospitality | 2025 |
| TY Golchi CYF | Wholesale & retail | 2011 |
| TY Gwyn Services Ltd | Administrative & support | 2022 |
| Tybed CYF | Education | 2020 |
| Tyddyn CAE Cyfyngedig | Agriculture & fishing | 2021 |
| Tyddyn MON Trading Ltd | Water & waste | 2011 |
| Tylers (Bangor) Limited | Information & communication | 1997 |
| Tymor Building Contractors Limited | Construction | 2002 |
| Tyson Wilson Ltd | Administrative & support | 2015 |
| Tyson Wilson Temp Limited | Administrative & support | 2019 |
| TZK Squad Ltd | Wholesale & retail | 2026 |
| U Local Limited | Wholesale & retail | 2020 |
| UAC Easter Stages Limited | Arts & recreation | 2018 |
| Ubreakirepair Ltd | Manufacturing | 2014 |
| Udevelopit C.I.C. | Education | 2015 |
| Uhub Therapy Centre | Health & social care | 2016 |
| UK American Sports Store Limited | Wholesale & retail | 2015 |
| UK Tyre Hub Ltd | Wholesale & retail | 2025 |
| Ukhab Ltd | Information & communication | 2020 |
| Ulster Angling Federation Limited-The | Arts & recreation | 1968 |
| Ulster Automobile Club Limited | Arts & recreation | 1955 |
| Ulster Tiger Properties Limited | Real estate | 2024 |
| Ultrasoundni Limited | Health & social care | 2024 |
| Undergrounddining Limited | Hospitality | 2015 |
| Unifi Software Development Ltd. | Information & communication | 2017 |
| Unit 6465 Ltd | Other services | 2025 |
| Unit Base Support Limited | Extraterritorial | 2022 |
| Unit Thirteen Ltd | Manufacturing | 2023 |
| United Energy Waste Management Ltd | Water & waste | 2021 |
| Unity Healthcare Staffing Ltd | Administrative & support | 2025 |
| Uplands Property Ltd | Real estate | 2025 |
| Urban Athletics Ltd | Arts & recreation | 2025 |
| Urban Invested Limited | Real estate | 2023 |
| Urban Office Space Holdings Limited | Financial services | 2023 |
| Urban Office Space Ltd | Real estate | 2019 |
| Urban Trek LLP | | 2010 |
| Urbn Eats Ltd | Hospitality | 2025 |
| V Edwards Coal Merchants Limited | Wholesale & retail | 2025 |
| V Francis Building Contractor Limited | Construction | 2022 |
| Validata Ltd | Information & communication | 2021 |
| Valor Combat Series Limited | Administrative & support | 2025 |
| Vandikson Ltd | Wholesale & retail | 2021 |
| Vapemeisteruk Ltd | Wholesale & retail | 2015 |