| Tedcom Limited | Information & communication | 2019 |
| Teer & Johnson Fisheries Limited | Wholesale & retail | 2007 |
| Tees Valley Smartzone Limited | Transport & logistics | 2018 |
| Teesside Air Supply Ltd | Other services | 2020 |
| Teesside and District Chamber of Commerce and Industry Limited | Professional & scientific | 1994 |
| Teesside Architectural Supplies Ltd | Professional & scientific | 2024 |
| Teesside International Development Limited | Construction | 2019 |
| Teesside International Land Limited | Construction | 2019 |
| Teesworks Limited | Water & waste | 2019 |
| Teesworks Port Limited | Extraterritorial | 2021 |
| Teesworks Quay Limited | Extraterritorial | 2021 |
| Tegan LLC Limited | Wholesale & retail | 2024 |
| Tehellim Ltd | Hospitality | 2026 |
| Tejay's Horseboxes Limited | Manufacturing | 2020 |
| Tekku Ltd | Professional & scientific | 2023 |
| Tekna Limited | Information & communication | 2008 |
| Telink Limited | Professional & scientific | 2026 |
| Terra Firma Surfacing Contractors Ltd | Construction | 2014 |
| Terravetus Holdings Ltd | Agriculture & fishing | 2026 |
| Terravetus Ltd | Agriculture & fishing | 2025 |
| Terry and Annis Hairdressing Ltd | Other services | 2006 |
| Terry Deary Limited | Arts & recreation | 1998 |
| Terry Property Holdings Ltd | Real estate | 2026 |
| Tessellate Ltd | Information & communication | 2025 |
| Tgya Global Ltd | Wholesale & retail | 2025 |
| Thames Group Investments Ltd | Financial services | 2025 |
| Thames Group Real Estate Ltd | Financial services | 2025 |
| Thames Group Services Ltd | Financial services | 2025 |
| Tharana Superstore Ltd | Wholesale & retail | 2025 |
| That Offers Site Ltd | Information & communication | 2026 |
| That Travel Cmpy Limited | Administrative & support | 2025 |
| THE Acquire Group London Limited | Professional & scientific | 2015 |
| THE Aesthetic Surgery North East Limited | Other services | 2022 |
| THE Alchemist Hair Salon Ltd | Other services | 2023 |
| THE Allotment Project CIC | Education | 2020 |
| THE Animal Superstore Ltd | Wholesale & retail | 2021 |
| THE Ballinger Charitable Trust | Administrative & support | 2007 |
| THE Banks Group Benefit Trust Company Limited | Financial services | 1989 |
| THE Banks Group Limited | Professional & scientific | 1988 |
| THE Barber of Neville Ltd | Other services | 2014 |
| THE Bay Horse by Watson Ltd | Hospitality | 2023 |
| THE Beauty Crew (TBC) Limited | Wholesale & retail | 2021 |
| THE Beauty Lounge Durham Ltd | Other services | 2023 |
| THE Beehive at High Shincliffe Ltd | Hospitality | 2026 |
| THE Beldav Group Ltd | Real estate | 2018 |
| THE Bishops Lodge PUB Company Ltd | Hospitality | 2024 |
| THE Boba Lounge Ltd | Hospitality | 2025 |
| THE Breakdown Doctor Limited | Professional & scientific | 1997 |
| THE Bridge Durham Ltd | Hospitality | 2026 |
| THE British Machine Vision Association & Society for Pattern Recognition | Professional & scientific | 1990 |
| THE British Sociological Association | Other services | 1999 |
| THE Caravan Lock People Ltd | Wholesale & retail | 2021 |
| THE Cherry Kearton Archive Ltd | Wholesale & retail | 2009 |
| THE City Bar Durham Limited | Hospitality | 2021 |
| THE Clan North East Ltd | Real estate | 2022 |
| THE Claypath Delicatessen Limited | Hospitality | 2010 |
| THE Clean and Reseal MAN Limited | Construction | 2022 |
| THE Coaching Accountant Limited | Professional & scientific | 2024 |
| THE Coffee House DH1 Limited | Wholesale & retail | 2019 |
| THE Coin Toss Ltd | Wholesale & retail | 2024 |
| THE Copper Kettle NE Limited | Hospitality | 2023 |
| THE Coronation Press Limited | Manufacturing | 2000 |
| THE Coshey Trade Ltd | Wholesale & retail | 2025 |
| THE Curious MR FOX Durham Ltd | Hospitality | 2024 |
| THE Damp Doctor Ltd | Construction | 2018 |
| THE Darby Rimmer MND Foundation | Other services | 2019 |
| THE Dentmaster (Durham) Limited | Wholesale & retail | 2018 |
| THE Detective Rooms Limited | Information & communication | 2024 |
| THE Dillon Group Limited | Financial services | 2025 |
| THE Drake Hotel Ltd | Hospitality | 2025 |
| THE Dreadnought (ESH Winning) Ltd | Hospitality | 2026 |
| THE Dreadnought (NE) Ltd | Hospitality | 2024 |
| THE Dromonby Group Limited | Financial services | 2019 |
| THE Drum Shed Ltd | Education | 2026 |
| THE DUN COW (Durham) Limited | Hospitality | 2014 |
| THE Dunelm Foundation Limited | Health & social care | 2019 |
| THE Durham BID Company Limited | Other services | 2010 |
| THE Durham Brewery Limited | Manufacturing | 1997 |
| THE Durham Centre Limited | Administrative & support | 2006 |
| THE Durham County Federation of Women's Institutes | Other services | 1992 |
| THE Education Partnership (UK) Ltd | Education | 2000 |
| THE Empathy Garden CIC | Other services | 2025 |
| THE Enchanted Cafe Ltd | Hospitality | 2024 |
| THE Excel Academy Partnership | Education | 2011 |
| THE Extendables Group Ltd | Construction | 2024 |
| THE Extendables Ltd | Construction | 2019 |
| THE Face and Body Clinic by Auton Ltd | Other services | 2018 |
| THE Farmyard Padel Club Limited | Arts & recreation | 2026 |
| THE Fitness LAB Durham Ltd | Arts & recreation | 2018 |
| THE Florist Shop (Durham) Limited | Wholesale & retail | 2018 |
| THE Forge Washington Ltd | Hospitality | 2024 |
| THE Friends of the Durham Miners' Gala Limited | Administrative & support | 2015 |
| THE Funky Mallard PUB Company Limited | Hospitality | 2026 |
| THE Gallus Edge CIC | Professional & scientific | 2019 |
| THE Garage Bar & Grille Limited | Hospitality | 2016 |
| THE Geordie PIE Company Limited | Hospitality | 2019 |
| THE Gherkin Group Limited | Professional & scientific | 2022 |
| THE Glow Group (NE) Ltd | Other services | 2024 |
| THE Golden Asanka Group Limited | Wholesale & retail | 2026 |
| THE Gourmet Bear Ltd | Manufacturing | 2025 |