| THE Pheasant Hotel (Harome) Limited | Hospitality | 2022 |
| THE Piercing Lady Darlington Ltd | Other services | 2025 |
| THE Printworks Management Company Limited | Households | 2002 |
| THE Property Paradox Limited | Real estate | 2020 |
| THE Property Thing Ltd | Administrative & support | 2019 |
| THE Radio Place Limited | Professional & scientific | 2015 |
| THE Radon Consultants Ltd | Professional & scientific | 2019 |
| THE Red Beard Barber Co Ltd | Other services | 2020 |
| THE Redeemed Christian Church of GOD Habitation of Hope Ltd | Other services | 2024 |
| THE Residents of Skerningham Management Company Limited | Professional & scientific | 2007 |
| THE Retail Practice Limited | Administrative & support | 2010 |
| THE Rich Co Europe Limited | Wholesale & retail | 2020 |
| THE RIO Pizza Ltd | Hospitality | 2024 |
| THE Rio's Limited | Hospitality | 2019 |
| THE Robin Centres (NE) Limited | Health & social care | 2018 |
| THE Rockup Project Ltd | Information & communication | 2025 |
| THE Rudman Group Limited | Professional & scientific | 2024 |
| THE Rustic Booth Company Limited | Professional & scientific | 2019 |
| THE Sewing Room Darlington Ltd | Other services | 2024 |
| THE Ship Sports Bar Limited | Hospitality | 2015 |
| THE Shiremoor Press Limited | Manufacturing | 2005 |
| THE Single USE Paper Company Limited | Wholesale & retail | 2018 |
| THE Social & Kitchen Ltd | Extraterritorial | 2023 |
| THE Social Media Consultancy Ltd | Information & communication | 2012 |
| THE Specialized Project CIC | Information & communication | 2021 |
| THE Square PEG Brewery Limited | Professional & scientific | 2010 |
| THE Stables (Wynyard) Limited | Hospitality | 2007 |
| THE Stephenson Locomotive Society | Other services | 2016 |
| THE Straightspeaking Partnership LLP | | 2012 |
| THE Strays Building Services Ltd | Construction | 2024 |
| THE Strays Developments Ltd | Real estate | 2020 |
| THE Structural Detailing Company (2009) Limited | Professional & scientific | 2009 |
| THE Stuffed Olive Limited | Hospitality | 2018 |
| THE Sweet Spot North Ltd | Wholesale & retail | 2026 |
| THE Thornaby Old Dairy (Management) Limited | Households | 2007 |
| THE Trusted Company (England) Ltd | Information & communication | 2017 |
| THE Union Arms 2023 Ltd | Hospitality | 2023 |
| THE Unknown Creative Limited | Professional & scientific | 2009 |
| THE V4 Steam Locomotive Company Limited | Manufacturing | 2005 |
| THE VAT Ready Club Limited | Professional & scientific | 2024 |
| THE Verve Foundation Ltd | Education | 2021 |
| THE VIC WLW Limited | Hospitality | 2019 |
| THE Vich GCP Consultancy Limited | Professional & scientific | 2022 |
| THE Viking Boat Company CIC | Administrative & support | 2021 |
| THE Virtual Collab Ltd | Administrative & support | 2026 |
| THE Voices Games Ltd | Information & communication | 2012 |
| THE Voices Group Ltd | Education | 2024 |
| THE Waggon Inn Ltd | Hospitality | 2018 |
| THE Wandering Duck Limited | Hospitality | 2016 |
| THE Weekend Connoisseur Ltd | Construction | 2019 |
| THE Wheatsheaf PUB 2017 Limited | Hospitality | 2017 |
| THE Wheatsheaf Staindrop Ltd | Hospitality | 2014 |
| THE Wilder Foundation | Health & social care | 2026 |
| THE Window GUY Ltd | Construction | 2019 |
| THE WM Morrison Darlington Enterprise Trust | Health & social care | 2010 |
| THE Woodologist Ltd | Manufacturing | 2024 |
| THE Woodshed Timber Ltd | Agriculture & fishing | 2022 |
| THE Works Building & Construction Ltd | Construction | 2018 |
| THE Write One NE Ltd | Professional & scientific | 2023 |
| THE Writers Table Limited | Education | 2026 |
| The-Gate-Company Ltd | Extraterritorial | 2011 |
| Thehempco Ltd | Extraterritorial | 2021 |
| Thelambton Limited | Hospitality | 2018 |
| Therapy Hair & Beauty (Wynyard) Ltd | Other services | 2017 |
| Thermal Insulation Contractors Association | Education | 1985 |
| This Host Ltd | Wholesale & retail | 2020 |
| Thistle Solutions Limited | Construction | 2013 |
| Thomas Andrew Sports Consultancy Ltd | Education | 2016 |
| Thomas Paul Harrison Logistics Ltd | Transport & logistics | 2025 |
| Thomas Paul Limited | Wholesale & retail | 2025 |
| Thomas Wright Management Company Limited | Households | 1989 |
| Thomasina Jean Merchandising Limited | Wholesale & retail | 2020 |
| Thompson Bros Limited | Construction | 2026 |
| Thompson Imports Limited | Wholesale & retail | 2026 |
| Thorngate Mill Management Company Limited | Households | 2004 |
| Thorngate Place Properties Limited | Real estate | 2005 |
| Three Horseshoes Washington Ltd | Hospitality | 2020 |
| Three Sisters Creations Limited | Wholesale & retail | 2020 |
| Thrive Coaching (Change, Grow, Purpose) Ltd | Professional & scientific | 2026 |
| Thrive Marketing Limited | Administrative & support | 2013 |
| Throttleworks ATV Ltd | Professional & scientific | 2026 |
| Thumbs UP Marketing Consultancy Ltd | Professional & scientific | 2020 |
| Thurlwell Engineering Ltd | Construction | 2025 |
| Thurston Construction Ltd | Construction | 2019 |
| Thysis Extrusions Ltd | Manufacturing | 2018 |
| Tica Certification Limited | Construction | 2025 |
| Tidy Masters Ltd | Administrative & support | 2018 |
| Tigazoju Ltd | Real estate | 2025 |
| Tiger Lettings Limited | Real estate | 2018 |
| Tigerdove Ltd | Professional & scientific | 2022 |
| Tile & Timber Ltd | Administrative & support | 2026 |
| Tillie Cole Ltd | Information & communication | 2017 |
| TIM Fabrication Ltd | Manufacturing | 2021 |
| Timber Brothers Limited | Wholesale & retail | 2017 |
| Time OUT Space Ltd | Wholesale & retail | 2018 |
| Times Cafe Ltd | Hospitality | 2024 |
| Timla Developments Limited | Construction | 2015 |
| Timla Limited | Manufacturing | 1988 |
| Timstrad Ltd | Other services | 2023 |
| TIN HAT Properties Limited | Real estate | 2023 |