| Truckparts (NE) Ltd | Wholesale & retail | 2017 |
| True North Interiors Ltd | Manufacturing | 2018 |
| Trunghao Estate Agent Ltd | Construction | 2023 |
| Trusted People Limited | Other services | 2021 |
| Trustflow Systems Limited | Information & communication | 2026 |
| Truth Digital NE Limited | Information & communication | 2021 |
| Truth Skills Ltd | Professional & scientific | 2024 |
| TS Holdings (North East) Limited | Real estate | 2020 |
| TS Media & Marketing Ltd | Information & communication | 2024 |
| TSM Window Cleaners Ltd | Administrative & support | 2019 |
| TSU Holdings Limited | Financial services | 2024 |
| TSU Limited | Construction | 2013 |
| TT Elecmech Limited | Manufacturing | 2011 |
| TT Kitchen Installations Limited | Construction | 2016 |
| TU Nova Education Limited | Arts & recreation | 2019 |
| Tuarex Ltd | Transport & logistics | 2021 |
| Tubular Frames Ltd | Manufacturing | 2019 |
| Turbocharger Solutions Limited | Wholesale & retail | 2012 |
| Turf Technical Ltd | Other services | 2016 |
| Turn 2 Sport Limited | Arts & recreation | 2021 |
| Turn Left Ventures Ltd | Professional & scientific | 2010 |
| Turners of Sedgefield Limited | Real estate | 1984 |
| Turquoise Beauty Limited | Other services | 2019 |
| Turquoise Medical Consulting Limited | Education | 2024 |
| Tutomi Limited | Education | 2025 |
| Tutor Village 2 Limited | Education | 2023 |
| Tutor Village Limited | Education | 2022 |
| TVP Group Ltd | Manufacturing | 2025 |
| Twalk CIC | Health & social care | 2025 |
| Tweddle Construction Limited | Construction | 2006 |
| TWF Consultants PTE Ltd | Professional & scientific | 2021 |
| TWF Properties PTE Ltd | Real estate | 2021 |
| Twin Scaffold Ltd | Construction | 2021 |
| Two Tykes Limited | Other services | 2019 |
| Twosab Ltd | Transport & logistics | 2021 |
| Tyber Enterprise Limited | Professional & scientific | 2016 |
| Tyne Tees Crushing & Screening Limited | Water & waste | 2005 |
| Tyne Tees Plant Hire Limited | Financial services | 2012 |
| Tyneside Agency Group Limited | Financial services | 2021 |
| Tyre Corner Ltd | Wholesale & retail | 2021 |
| U&I Digital Ltd | Information & communication | 2019 |
| Ucalypt Remi Limited | Wholesale & retail | 2022 |
| Ufuel Ltd | Manufacturing | 2025 |
| UID Link Ltd | Professional & scientific | 2024 |
| UK Adventure Holdings Ltd | Financial services | 2025 |
| UK Drivers Club Ltd | Wholesale & retail | 2024 |
| UK Field Marketing Limited | Professional & scientific | 2013 |
| UK Globalfinance Ltd | Arts & recreation | 2021 |
| UK NI Transport Ltd | Transport & logistics | 2022 |
| UK Off-Road Limited | Wholesale & retail | 2026 |
| UK Renewable Experts Ltd | Wholesale & retail | 2020 |
| UK Scaffold Limited | Construction | 2020 |
| UK Web Geekz Ltd | Information & communication | 2015 |
| Ulnaby Hall Farm Limited | Professional & scientific | 2012 |
| Ultimate Artists Limited | Arts & recreation | 2012 |
| Ultimate Grooming Darlington Ltd | Other services | 2024 |
| Ultramarine Consulting Limited | Mining & quarrying | 2009 |
| Ultraspray Limited | Wholesale & retail | 2001 |
| Understanding Minds LLP | | 2026 |
| Underwater Drone Systems Limited | Professional & scientific | 2012 |
| Uniq London Ltd | Wholesale & retail | 2019 |
| Uniq Recording Artists Limited | Information & communication | 2018 |
| Unique Car Sale Ltd | Wholesale & retail | 2018 |
| Unique Doors and Shutters Limited | Construction | 2018 |
| Unique Electrical Engineers Ltd | Administrative & support | 2016 |
| Unique Roofs Limited | Construction | 2016 |
| Unisolo Limited | Wholesale & retail | 2023 |
| United Quantum Ltd | Professional & scientific | 2019 |
| Unitsixteen Automotive Ltd | Wholesale & retail | 2017 |
| Univibe Limited | Professional & scientific | 2025 |
| UNO Momento Boro Ltd | Hospitality | 2014 |
| UNO Momento Darlington Ltd | Hospitality | 2011 |
| UNO Momento Middlesbrough Ltd | Hospitality | 2019 |
| UNO Yarm Ltd | Hospitality | 2024 |
| Unportan Ltd | Wholesale & retail | 2025 |
| Unrivalled Heating Ltd. | Construction | 2015 |
| Untitled NO 1 Limited | Wholesale & retail | 2020 |
| Untrodden Expeditions CIC | Administrative & support | 2023 |
| Unwind in France Ltd | Households | 2025 |
| UP & Go MAN & Van Ltd | Transport & logistics | 2024 |
| UP North Electrical Solutions Ltd | Construction | 2019 |
| Upbeatdata Ltd | Information & communication | 2012 |
| Upex Properties Limited | Real estate | 1996 |
| Uplands Court (Darlington) Residents' Association Limited | Households | 1992 |
| Upperthorpe Nursery Ltd | Health & social care | 2014 |
| Upright Limited | Construction | 1984 |
| Uptax Ltd | Professional & scientific | 2023 |
| Upton MOT Ltd | Wholesale & retail | 2020 |
| Upvc Care & Repair Ltd | Construction | 2023 |
| Urban Farm Mushrooms Ltd | Manufacturing | 2024 |
| Urban OPS Limited | Wholesale & retail | 2025 |
| Urbansuite Ltd | Administrative & support | 2017 |
| URW Group Ltd | Other services | 2024 |
| Uryk Dmyterko Ltd | Manufacturing | 2023 |
| Usher Installations Ltd | Extraterritorial | 2018 |
| V-Ape International Ltd | Wholesale & retail | 2018 |
| Vad&Ina Ltd | Transport & logistics | 2020 |
| Valcryon Ltd | Manufacturing | 2026 |
| Valente Developments Limited | Hospitality | 2003 |
| Valentin Dobre Logistics Limited | Transport & logistics | 2026 |