| T.K. Brolly Enterprises Limited | Other services | 1978 |
| T.S.I. (Ireland) Ltd | Information & communication | 1998 |
| Tailored Facility Solutions Limited | Administrative & support | 2017 |
| Take IT Easy Homes Limited | Real estate | 2008 |
| Talbot Projects Ltd | Real estate | 2017 |
| Talbot Ventures Limited | Real estate | 2010 |
| Tancy YUL Limited | Wholesale & retail | 2025 |
| Tark Electrical Ltd | Construction | 2021 |
| Tarn Technologies Ltd | Information & communication | 2003 |
| Tasawar Cendycloud Limited | Wholesale & retail | 2024 |
| Tawnymore Limited | Construction | 2006 |
| TAX4TECH Ltd | Professional & scientific | 2021 |
| TCG Hotels Ltd | Hospitality | 2026 |
| TCG Investments Ltd | Real estate | 2026 |
| TCS Healthcare Ltd | Wholesale & retail | 2014 |
| TD MCC Ltd | Hospitality | 2022 |
| Teamworks Community Maintenance C.I.C. | Administrative & support | 2014 |
| Tearri DFB Ltd | Wholesale & retail | 2023 |
| Tedley Lane Ltd | Households | 2024 |
| Teeavan Holdings Limited | Financial services | 2026 |
| Teeavan Interiors Limited | Construction | 2018 |
| Temp Electrix Limited | Extraterritorial | 2013 |
| Templemoyle Construction Limited | Construction | 2018 |
| Templemoyle Farm Ltd | Agriculture & fishing | 2015 |
| Tempting Places Limited | Real estate | 2020 |
| Terra North West Limited | Construction | 1999 |
| THE Artistry Lounge Ltd | Real estate | 2025 |
| THE Bentley Bar (Derry) Ltd | Hospitality | 2011 |
| THE Bentley Group Security Ltd | Administrative & support | 2018 |
| THE Black TIE Showroom Limited | Wholesale & retail | 2006 |
| THE Bogside Tavern Trading AS 7 Twenty Bar Ltd | Hospitality | 2025 |
| THE Brow Bar Derry Limited | Other services | 2026 |
| THE Burn PIT Lounge Ltd | Hospitality | 2024 |
| THE Cosh Bar Ltd | Hospitality | 2014 |
| THE CUT Restaurants Limited | Hospitality | 2025 |
| THE Danesfort Cafe Ltd | Hospitality | 2022 |
| THE ELEV8LAW Group Limited | Professional & scientific | 2019 |
| THE Embankment Derry Ltd | Hospitality | 2018 |
| THE Explorer App Team Ltd | Information & communication | 2026 |
| THE Faughan Valley CIC | Education | 2023 |
| THE Frozen Food Store (2010) Ltd | Manufacturing | 2018 |
| THE Fuel Shed Limited | Wholesale & retail | 2018 |
| THE Giddy Goat Ltd | Hospitality | 2019 |
| THE Global Warriors Movement Ltd | Information & communication | 2026 |
| THE Golden Chipper Ltd | Hospitality | 2018 |
| THE Hillocks Management Limited | Real estate | 2018 |
| THE Hills Church Ltd | Other services | 2017 |
| THE Influencer Hub Marketplace Ltd | Administrative & support | 2024 |
| THE Jasminade Ltd | Hospitality | 2019 |
| THE Junction: Community Relations and Peace Building | Other services | 2015 |
| THE Little Paper Gift Co Ltd | Wholesale & retail | 2024 |
| THE Magnet Bar (Derry) Ltd | Hospitality | 2014 |
| THE Maiden City Festival | Arts & recreation | 2002 |
| THE Mclaughlin Group Limited | Construction | 2016 |
| THE Mortgage Lounge Limited | Financial services | 2026 |
| THE Nail Studio Derry Ltd | Other services | 2015 |
| THE Nerve Centre Ltd | Arts & recreation | 1997 |
| THE OUI Bakery Ltd | Manufacturing | 2024 |
| THE Play Shed (UK) Limited | Arts & recreation | 2014 |
| THE Pram Centre (Derry) Limited | Wholesale & retail | 2003 |
| THE Pregnancy Coach Ltd | Health & social care | 2020 |
| THE Promotion Group Ltd | Other services | 2022 |
| THE Question IS Productions Ltd | Arts & recreation | 2023 |
| THE Rhino Range Ltd | Wholesale & retail | 2017 |
| THE Rice Bowl (Derry) Ltd | Hospitality | 2016 |
| THE Rice Bowl Drumahoe Ltd | Hospitality | 2017 |
| THE Ryan Mcbride Foundation | Education | 2017 |
| THE Sandwich Co (Spencer Road) Ltd | Hospitality | 2012 |
| THE Sandwich CO.1 Ltd | Hospitality | 2017 |
| THE Siege Museum Limited | Arts & recreation | 2003 |
| THE Sleepy Teepee Club Ltd | Households | 2019 |
| THE Spirit Circle Limited | Hospitality | 2026 |
| THE Sugaring Salon Ltd | Other services | 2021 |
| THE Suit Lounge Ltd | Wholesale & retail | 2017 |
| THE Tanning Rooms (NI) Ltd | Other services | 2016 |
| THE Tyre Depot Derry Limited | Wholesale & retail | 2023 |
| Thecountrysideview Ltd | Hospitality | 2023 |
| Thelightspace Ltd | Arts & recreation | 2021 |
| Thermal Garden Ltd | Other services | 2026 |
| Thermech UK Ltd | Construction | 2024 |
| Thestorefront Ltd | Wholesale & retail | 2019 |
| Thinkpod Studios Limited | Information & communication | 2026 |
| Thjmcd Ltd | Information & communication | 2015 |
| Thomas Conner Limited | Manufacturing | 2024 |
| Thomas Patrick Recruitment Limited | Professional & scientific | 2025 |
| Thompson & Mcgeady Limited | Real estate | 1964 |
| Thomson Property Management Limited | Real estate | 2024 |
| Three Keys Living Ltd | Hospitality | 2025 |
| Threepines Limited | Real estate | 2002 |
| Tidal Holdings Limited | Financial services | 2002 |
| Tiff Material Trading Ltd | Wholesale & retail | 2025 |
| Tile Image Ltd | Wholesale & retail | 1999 |
| Tileline Group Limited | Wholesale & retail | 2024 |
| Timber KIT Buildings Limited | Construction | 2021 |
| Timber KIT Competitions Limited | Construction | 2021 |
| Time for EWE CIC | Health & social care | 2023 |
| Timeless Moments Investments Limited | Financial services | 2026 |
| TIN Town Music Ltd | Hospitality | 2014 |
| TIP Top Roofing & Building Services Ltd | Construction | 2025 |
| Tirkeeran Trading Ltd | Construction | 2020 |