| Steadfast Installations Limited | Construction | 2022 |
| Steadfast Secure Storage Ltd | Other services | 2007 |
| Steadfast Security Group Limited | Administrative & support | 2009 |
| Steadfast Security Limited | Public administration | 2021 |
| Steadfast Security Solutions Limited | Administrative & support | 2010 |
| Steadfast Security Systems Ltd | Administrative & support | 1997 |
| STK Offshore Services Ltd | Construction | 2024 |
| Studio 48 Ltd | Information & communication | 2011 |
| Subvectra Technologies Ltd | Manufacturing | 2026 |
| Sugar Rush Express Ltd | Hospitality | 2026 |
| Sugar Rush the Sweet Life Ltd | Hospitality | 2022 |
| Sunderland Car Wash Ltd | Administrative & support | 2025 |
| Sunshine Day Nursery (Peterlee) Limited | Other services | 2011 |
| Sunshine Day Nursery at Seascape and Dene House Peterlee Limited | Other services | 2011 |
| Supreme Property Management Limited | Real estate | 2018 |
| Supreme Staycations Ltd | Construction | 2024 |
| Sure Trades People Limited | Wholesale & retail | 2026 |
| Sweth Limited | Professional & scientific | 2022 |
| SWS Outsourcing Limited | Professional & scientific | 2024 |
| T & M Fabrications Ltd | Manufacturing | 2020 |
| T.E.R.M. Group Ltd | Real estate | 2025 |
| T.I.F Consultancies Ltd | Professional & scientific | 2023 |
| T.W.R. Trade Frames Limited | Manufacturing | 2004 |
| TAN & Cafe Limited | Arts & recreation | 2025 |
| Taxpro Solutions Ltd | Professional & scientific | 2014 |
| TD Courier Services Limited | Transport & logistics | 2019 |
| Tds-Uk Ltd | Professional & scientific | 2023 |
| Tees Valley Transport Ltd | Transport & logistics | 2022 |
| Teesworks Cladding Co Limited | Construction | 2022 |
| Tel-Net TS Ltd | Information & communication | 2021 |
| Telc Telecoms Ltd | Information & communication | 2023 |
| Temporary Power Ltd | Professional & scientific | 2026 |
| Thalyn Pryndel Limited | Wholesale & retail | 2026 |
| THE Barn at Easington | Arts & recreation | 2013 |
| THE Bath Fitting Company Limited | Construction | 2022 |
| THE Bathroom Cladding Company Ltd | Construction | 2020 |
| THE Bell Guesthouse Ltd | Hospitality | 2024 |
| THE College Company Limited | Education | 1993 |
| THE Commercial Investigation Bureau Limited | Administrative & support | 2019 |
| THE East Durham Employability Trust | Education | 2011 |
| THE Fulfilment Experts Limited | Transport & logistics | 2022 |
| THE Leather CAP Sports and Social Club Limited | Other services | 2015 |
| THE Moorcock (Peterlee) Limited | Hospitality | 2012 |
| THE New VIC Ltd | Hospitality | 2017 |
| THE Play Place U.K. Ltd | Hospitality | 2018 |
| THE Uneek Brand Limited | Wholesale & retail | 2025 |
| THE Whistling Teapot C.I.C. | Hospitality | 2018 |
| THE Woolly Witch Ltd | Wholesale & retail | 2026 |
| Thompsons Tackle Supplies Ltd | Wholesale & retail | 2025 |
| Thyssenkrupp Rothe Erde UK Ltd. | Manufacturing | 1975 |
| Tillyer Logistics Limited | Transport & logistics | 2025 |
| Tiny Town Play Ltd | Arts & recreation | 2025 |
| Titan Meats Limited | Manufacturing | 2026 |
| TKS Reviews Ltd | Health & social care | 2025 |
| TMT Plastering Contractors Ltd | Construction | 2009 |
| Tomorrow Holdings Ltd | Financial services | 2025 |
| Tonks 2000 Limited | Water & waste | 2000 |
| Top Deck Events Ltd | Administrative & support | 2025 |
| Total Windows, Doors and Solar Ltd | Construction | 2026 |
| Tower Bridge Bakery Group Limited | Financial services | 2025 |
| TOX 247 Limited | Administrative & support | 2016 |
| Training Assessment & Consultancy Services Limited | Education | 2007 |
| Training Support for Industry Limited | Administrative & support | 2006 |
| Tranquil Talent Group Ltd | Professional & scientific | 2024 |
| Tray Cafe Ltd | Hospitality | 2024 |
| Tree Wise MEN (NE) Ltd | Agriculture & fishing | 2022 |
| Triple-R Performance Ltd | Wholesale & retail | 2022 |
| Truly Yours Limited | Wholesale & retail | 2005 |
| Turnbull Roofing Ltd | Construction | 2025 |
| Turntech Ltd | Manufacturing | 2021 |
| UK Utilities Limited | Energy | 2017 |
| Ulifoods Limited | Manufacturing | 2025 |
| Uligames Limited | Information & communication | 2025 |
| Ulihomes Limited | Construction | 2026 |
| Ultimate Holdings Group Limited | Real estate | 2019 |
| Understify Ltd | Information & communication | 2026 |
| Urban Autocare (Peterlee) Ltd | Wholesale & retail | 2026 |
| Urwin Online Ltd | Wholesale & retail | 2024 |
| Utilities Services Ltd | Extraterritorial | 2015 |
| Uyan Hair Ltd | Other services | 2025 |
| Vaelthyr Mornox Limited | Wholesale & retail | 2026 |
| Valet Centre UK Ltd | Other services | 2017 |
| Van-Lidz Ltd | Manufacturing | 2019 |
| Vape & Beyond Ltd | Wholesale & retail | 2025 |
| Vape Peterlee Limited | Wholesale & retail | 2016 |
| Vapourlites Limited | Manufacturing | 2011 |
| Verre World Ltd | Wholesale & retail | 2026 |
| Vestas Aircoil UK North Ltd | Wholesale & retail | 2026 |
| VMI Haulage Limited | Transport & logistics | 2017 |
| VMI Technology Ltd | Information & communication | 2026 |
| W S Surfacing Ltd | Construction | 2025 |
| W.L and L Ltd | Other services | 2016 |
| Wallace Property Investment (2017) Limited | Real estate | 2017 |
| Ward Martelle Limited | Administrative & support | 2011 |
| Waterstone Bathrooms Limited | Construction | 2025 |
| Wavecon Ltd | Manufacturing | 2020 |
| Wayne's World Ltd | Information & communication | 2020 |
| Wear Developments Ltd | Construction | 2021 |
| Wfifs Ltd | Professional & scientific | 2026 |
| Wheatley Commissioning Services Limited | Manufacturing | 2012 |